Um... perhaps I made a mistake in taking a light-hearted tone on what could be a very serious subject. I do not consider that any of the possibilities that I mentioned are out of the question. OK.... I was joking about the anal probes... and the Denebian oysters...

The military one is also a bit unlikely... but not impossible. Those four were just of the top of my head.... there truly are many possible reasons why a alien species may wish us harm.

It is often said (as a sort of religious chant) that a truly technologically advanced species would be enlightened and beneficent. (Assuming that only a technologically advanced species would have the wherewithal to build interstellar craft.... which is an assumption that can be argued against...) I personally find it amazing that people as worthy of respect as Carl Sagan and many others can, (or did,) hold such an unjustified view.

There is nothing inherently moral in advanced technology... just a modicum of intelligence, a society that in some way, (it doesn't need to encourage it...,) allows for the possibility of scientific advancement, and oodles of time will get you there. Considering that the universe has been around for 13 plus billion years, and 3rd gen stars for most of that time, statistically it is extremely unlikely that any co-existent species will be anything other than at least millions of years different in their stage of advancement.... irrespective of the as-yet-unknown likely period for life beginning.

I will agree that it is possible (and perhaps even likely) that advanced technology societies don't last long because they manage to annihilate themselves.... (we are a case in point perhaps)... but unless it is invariably so, it still may leave a large number of star faring species co-existent.

It is certainly possible to imagine societies that are semi-static for long, even staggeringly long, periods, (perhaps for overwhelmingly strong biological reasons for instance), but that time scale still would allow for massive technological differences.

Now you can say that this doesn't seem a matter for serious consideration... but if so, could you please point to the errors in my argument.

NoCleverName: Yes to us it would be a staggering, unlikely investment of our resources... but it may not be so to some other species. And as to whether or not we are a threat... now, or in their estimation of the possible future, that may not be the reason they wish us harm... they just might like a clean house without vermin... who knows. (And that is merely one of those gazillion (love that word) possibilities.

Think about it.... if nanotechnology and robotics and all the other gee-whiz technologies came to fruition, (even just a couple,) then any of us might in the far future have the capability (and time) to go relativistically off to nearby systems.... and at that point we might know quite a bit about them.

Now imagine redneck Billy-Joe with a high tech bazooka off 'hunting' the local systems for sport... unlikely yes.... impossible... no. And if it can be imagined... it likely has happened in a universe this big and old. Hopefully not now... or here...