I think that if an extraterrestrial high tech intelligence had discovered us, we wouldn't be here by now.

'Observe how these bipeds abuse their planet, war with each other, rape, torture, murder, abuse their children - heck, even sexually abuse their own children sometimes, AND waste their lives watching reality TV. These critters could be dangerous with the right technology in their hands.
Let's just irradiate their planet and leave it to the cock-roaches, come back in a million years and see if they have made a better job of things'.

But of course it is conceivable that the visitors are as uncivilised as us, and then we are still in trouble.

Blacknad.