Urges of this sort are an illness. Acting on those urges is a reprehensible criminal act.
I don't necessarily think goading people into taking action is OK, but I don't have a problem with anyone setting a trap either...I suppose it all boils down to the types of chats that the hunter has with these people, though I can't imagine him saying anything lewd or leading.
This feels to me as though he's busting people that succumb to their urges. Identifying them and flagging them is, well, welcomed. For those with the illness that don't act on it...they're not acting. They won't get caught, because they're not doing anything.
I think we should shame the act, not the illness. I can't speak to what kind of treatment should take place because I'm not a doctor, but I also don't have any issues with flagging a potential sexual abuser of children. And I take far more sympathy on the child than the pedophile. There's a line to be drawn, here.