I read a great article once. The title was "Kill them and eat them". The subtitle was "no matter how bad they taste". The gist was that anytime a technologically superior culture meets a technologically inferior culture the only ones that get left alone are the cannibals, most of whom are still being left alone while all the friendly Indians have been wiped out. So what we should do if we ever meet ETs is BBQ them and hopefully their friends will leave us alone because we are too disgusting to mess with. :)