(AP) -- British astrophysicist Stephen Hawking says aliens are out there, but it could be too dangerous for humans to interact with extraterrestrial life.The most convincing counter-argument to this, I think, is Gerard K O'Neill's argument from 2084:
Hawking claims in a new documentary that intelligent alien lifeforms almost certainly exist, but warns that communicating with them could be "too risky."
The 68-year-old scientist says a visit by extraterrestrials to Earth would be like Christopher Columbus arriving in the Americas, "which didn't turn out very well for the Native Americans."
He speculates most extraterrestrial life will be similar to microbes, or small animals - but adds advanced lifeforms may be "nomads, looking to conquer and colonize."
1) Destroying a non-spacefaring civilization would be pitifully easy for a society of even modest star-crossing abilities.
2) We have not been destroyed.
A) Aliens do not exist.
B) They exist, but are unable to harm us.
C) They exist, but are unwilling/not inclined to do so.
This isn't terribly hard thinking. I don't know how the Conquistador analogy is even supposed to work, really. There's literally nothing on Earth that would be worth the effort of taking that you couldn't get from the asteroid belt or outer solar system.