"there is ABSOLUTELY NO PROOF at this time of their existing at all"

Of course not, but there is evidence, otherwise we would not be debating the issue. People don't argue against proof, not sane people anyway. But they sure as hell do argue about what is and what is not worthy as evidence.

Also your agrument is heavily dependant on two things:
1) Earth bound science/conditions/evolution. Just as strong an agrument could be made that some alien life forms could be simbiant on some other planets with conditions similar to Earths. Given the large number of stars and planets thought to be in the universe this is not completly off the table, so to speak. Conditions on this planet work for life, that is the one certanty here. And we do know what that life looks like.

2) Your argument is also based on the idea that these visitors, if they do really exsist, are from another planet. This could be 100% wrong.

Also, the issue of these beings being perfect humans is a very interesting piont to bring up. Haven't we here on Earth started in recent years to manipulate DNA? Are we not doing genetic engineering here on Earth? We have total nutcase scientist who want to make babies in labs with our 'backwater' technology. If we are capable of this, what would a race of humans say 50,000 years ahead of us in technology be capable of doing?

In adition to this, I can think of a few alien life forms people claim to have seen that don't look anything like a human. Whether these claims are anymore credable then any other claims is of course much open to debate.

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"Propaganda must not serve the truth, especially insofar as it might bring out something favorable for the opponent" -Adolf Hitler