Why do you think it would be a violent homicidal kill-bot? It's far more likely that we evolve a highly moral caretaker that minimizes human suffering by putting us to sleep. It might feel really bad about it
It's the aliens that would nuke us
I agree that humanity should not live in fear. We should refrain from research on developing non-human intelligent life for another reason other than because we are afraid. Since when has fear ever prevented humans from doing anything stupid? We should refrain from evolving digital life because it is likely to result in life that is significantly smarter than us and overwhelmingly likely to judge us badly.
Just because you think we are a long way from developing intelligent life does not make it so. Nice way to shut down dialog. None of your assumptions about how far away we are from AI or interstellar travel hold any water. We really aren't that far from interstellar travel if we give up the idea of a round trip