That's my exact thinking. Why bother? But you wouldn't employ someone with criminal convictions, would you?
So he uses FB to check out Gay Guys and you want to report him to management as a criminal?
You had better have some significant proof of wrongdoing before you accuse someone of that kind of thing.
He is only 18 himself so unless you have evidence or a serious suspicion that he is grooming children I would suggest simply removing him from your FB friends list and leave it at that.