You're assuming that they'd even want to contact a violent, insane species like us.
Looking at us from a technologically superior extraterrestrial's viewpoint, we might well be worth studying or keeping an eye on, but open contact would probably be out of the question. Wouldn't want to risk being contaminated with whatever's infected us, you know?
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.