I was really interested in watching this as have a background of working with sexually exploited young people. Gratefulhead I think you've made the most eloquent and well argued responses on here and I agree with you wholeheartedly.
I also agree with the comment from Nancy above that there is slightly more to Stenson and his motives than meets the eye. I'm not saying he's getting a personal kick out of this but given the details he did give about his background, I would hazard a guess that abuse is something he may have had personal experience of. This is a horrific, sexualised world that he's choosing to spend time in. Those who work for CEOP, the Internet Watch Foundation and other such organisations a) have years of professional training and experience behind them and b) have access to support, counselling and the chance to reflect on what they're seeing and being exposed to every day.
Stinson has neither of these things and nor does he have a loving, supportive family of his own. This puts him at risk of being damaged by the world he's inhabiting and I don't think there will be a good outcome for him as a result of all this.
I'm not saying he's a bad person, far from it. It's clear that the work he's done has potentially saved some children from being abused.
But I do feel that there's a danger to himself from his work, and that the line between doing things for the right reasons / wrong reasons may become blurred without the right support for himself.