If they were technologically advanced enough to get here, I doubt we would be any threat to them, no matter how violent or insane we were. The Aztecs were violent and insane, but the Spanish had no problem subduing them and putting them to work for them.
Point taken, but we're just having an intellectual exercise here.
What would be the upside in making open contact with earthlings for an advanced extraterrestrial race? I can't think of any off the top of my head.