Inspired by the Why the aliens will be nice thread:

Reasons why aliens visiting us might not be nice:

-they don't think we're intelligent enough by their standards and therefore eradication does not matter
-they conclude we are an evolutionary cul-de-sac (hey, they could have the technology to determine that - or they are just space nazis) and need to be mercy-killed
-they can't communicate with us on any level nor can they imagine that we use different methods to communicate than they do (see Ender's Game for example)
-they simply don't care; they want a planet at this specific position to settle on.
-they see us as a potential threat and launch a preemptive strike before we evolve enough to be a bother
-they conclude through their observations that we are a warlike race that will never agree with their morals and need to be exterminated (similar to the above point)
-they think any technologically less advanced race is slave material
-they eat suns
-they eat planets
-they are not advanced at all, but parasites or predators that can survive in deep space (e.g. borg, body snatchers, alien etc.)
-they don't care about earth/us at all but use it as gambit in an interstellar turf war (if they are any like humans I'd say this is a rather likely scenario)

Any race advanced enough to make a propulsion able to span the distance between star systems in reasonable time has the energy to decisively win the war without even breaking a sweat. So has any race tough and long-lived enough to get around without such propulsion.

Any more takers?

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[Foot mouth in put]
Si tacuisses, philosophus mansisses.

I don't agree with the low intelligence thing. Low intelligence doesn't mean you don't have feelings.

-they have a religion and want to bring it to us, destroying those who won't believe.
-or, alternately, their religion requires the sacrifice or consumption of sentients, and they're overjoyed to use us instead of each other.
-they decide to enslave us for our own good (taking up the gray man's burden).
-they've found so many other civilizations and sentient life forms that they see no value in talking to yet another.
-they have technology that is fueled by souls and see us as merely a potential energy source (yeah, that one's kind of out there).

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"You miss 100% of the shots you don't take" - Wayne Gretzky

Tell that to the next bug you step on.

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Girl: Mister Darwin! The stupid people are breeding and taking over the planet!
Charles Darwin: Tut tut, little girl, don't worry! I'll take care of them with my CHAINSAW OF NATURAL SELECTION! Ahahahahahhaha!!!!!!
-QUeen of Wands 12/08/2003

Avid hunter and predator I may be, I don't stomp bugs even. If I find one, or a spider inside the house, I carry it outside.

I found a snake in my bathroom, got bitten three times getting it outside unharmed.

Even bees and wasps, I capture using a handy container and release outside.

Respecting the value of life is important to anyone that may be in a situation where they must take a life.
Whether it be to eat, defend or or even with humans in war or defense.


I also don't agree that a civilization that can travel in interstellar craft must automatically be able to declare war against an Entire Planet easily.

I can (technically) go faster than the speed of sound, but I cannot declare war on ... heck I was going to say Russia, but even Rhode Island!

The energy requirements and weaponry needed to take on 7.5 billion intelligent creatures would be phenomenal, and making an assumption that just because they can travel star to star that they must be able to attack billions seems like nonsense to me.

Well, humans ARE...

---war-like, and will fight over land, resources, ideology, and for pure spite and animosity.

---ecological menaces, prone to kill and consume all other living things within their own world, and pollute the entire ecosystem in the process.

---greedy SOBs who try to rob the weaker of their kind so that a few might prosper, if only briefly.




Any decent race who studies us for a while surely wouldn't want us gallivanting across the cosmos.
"Wha...? Humans? Oh, great! There goes the neighborhood!"

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Angel of the Abyss
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"I am Ripper...Tearer...Slasher...Gouger. I am the Teeth in the Darkness, the Talons in the Night. Mine is Strength...and Lust...and Power! I AM BEOWULF!"

I don't kill bugs either. They're alive, for Pete's Sake!

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Rovers forever! - ToSeek
"The only way to explore the universe is to go and look." - Brian Cox
Well, the best way to find out is to go there and, find out. - Raven's Cry
'Evolution and science are one thing, but you don’t mess with Yoko Ono. Everybody knows that. ' - 386sx

Hey, the religion thing is good, I completely missed that one.
I've got some more.

-they can't help it but are poisonous to us (think the first people who came to the american continent)
-they are allergic to us (same, but other way round)
-they wipe us out by accident (e.g. the tidal wave of their spacecraft kicks Earth around and sends us into another ice age, or burns us)

I'd say that if you have a drive that can generate a lot of energy (i.e. travel from star to star with energy left for a quick detour around Earth) you have a weapon. However you put it. Just accelerate a rock from the asteroid belt enough to put it on a collision orbit, or see above...

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[Foot mouth in put]
Si tacuisses, philosophus mansisses.

So if somebody is less clever than you , you eradicate him/her ?
Why an evolutionary cul-de-sac need to be killed ? Why not enjoying it ? Put in in a zoo ? A reservation ? . . .
Only case i could agree . . . Maybe

Planets !! who want these messy things !! Badly climatized , full of bacteries and other nasty things ! You cannot steal a planet! Remember the last time Martians tried to steal our Earth how they were killed by our valiant microorganisms !
They don"t give a damn a bout us naked monkeys !
Slaves are only good for morons. No advanced race will use them.
-Not at all , they prefer ice creams !
Yours aliens are from Texas no ?

You get one thing wrong. I never said any of those opinions were mine. On the other hand I never assumed that aliens think like us or have a similar concept of morals. Actually, it might be unlikely.
I'd like nice aliens but I thought I'd just make a collection of reasons aliens could be nasty after we already made one why aliens could be nice.

Sure. If a mosquito annoys me I kill it without feeling bad. And if I have the flu, I want to get it out of my system as fast as possible! Yay for flu genocide!
(Note: I am vegetarian, though.)

Could be that they think it's useless to keep us alive. Or they see themselves as executors of Darwin's law. Or they think of themselves as breeders of all the other races, maybe they even have seeded this planet long ago (a while later they wiped out the dinosaurs because they weren't happy with the direction they were going in...).

Pfft, nothing a good nuking from orbit could not cure. Come back in a few millennia and all will be fresh for moving in.

Abbadonn_2008 put it rather well, exactly what I was thinking.

But they're so fashionable... especially those adorable monkeys.

Actually, they think humans taste just scrumptious.

Naw, much smarter than that.

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[Foot mouth in put]
Si tacuisses, philosophus mansisses.

They will flood us with their homogenised fast-food chains, music, and reality shows, wiping out our local Earth traditions. Our multinationals will be put out of business by the cheaper output of their interstellar corporations, and they'll buy off our politicians so they can outsource their low-pay jobs to Earth. Their advertising, flooding all the media, will promote an esthetics based on green skin and antennas which will lead us to be frustrated with our looks and spend our money on cosmetics to dye our skin and antenna implants... Welcome to galacticalisation.

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"All your bias are belong to us." Ara Pacis
"A witty saying proves nothing." Voltaire

I like my antennae, FYI! The right one, if you note, is fully erect, giving the impression of keen wit and alertness. The left one is tilted slightly, so as to give the 'I'm too sexy and cool for hanging with you' vibe....because I am, of course.

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Angel of the Abyss
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"I am Ripper...Tearer...Slasher...Gouger. I am the Teeth in the Darkness, the Talons in the Night. Mine is Strength...and Lust...and Power! I AM BEOWULF!"

Expanding on this: they might be so alien they dont even recognise us as being alive and wipe us out by mistake, or we dont recognise them and do something to provoke them. Happy thoughts...

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For me it's enough for the garden to be beautifull; why do so many want to see fairies at the bottom?

They watched E.T. and are ****ed.

Wouldn't you be ****ed if you were portrayed that ugly?

But then they watched Star Trek and laughed so hard they calmed down.

Maybe their technology uses biological components and Earth is to be used as a lucrative place to mine for parts

If they wanted a fresh start on our planet they would have to eliminate more than just us. From a bio-mass perspective we are just a drop in the bucket on good old earth. They would have their hands full even after we were gone. From whales to micro-organisms, many animals would likely be lethal to them. Then again, they may already be here?? (sorry, that was a remnant of the woo in me, you know like the borg thing kind of)

Right, so they drop a few 100 km KBOs on the planet. A few bacteria might even be able to survive that, but it's questionable.

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I say there is an invisible elf in my backyard. How do you prove that I am wrong?

Disclaimer: Avatar is not an official NASA image and does not imply any specific interplanetary or interstellar capability.

The Leif Ericson Cruiser

Here's another scenario which is often overlooked:
all of the above is wrong, and aliens are actually extremely nice
(i.e. the moral standards of their civilization are extremely high)

There is still no guarantee though that this will mean anything to the party making first contact with us.

The ones who finally bump into us might be a rogue, pirate or shipwrecked vessel or fleet, not an official diplomatic mission.
They might be in desperate need of resources and not give a damn about what the rest of their civilization think anyway.