One of my tutors at college got 'poached' many years ago, to work on their anti-porn unit, it was his job to track down where someone was using their ISP address, and they would have a visit from the boys in blue. They would also track down the providers of such filth, and they'd have the book thrown at them, although they'd be out in a few months and back to making the hardcore stuff. They let the other inmates know what they'd been doing, and justice in it's most basic form is what they got once they were inside. The prison officers would let it go on, and stop it short of Murder, so most of their time was spent in Hospital Prison.
Interestingly enough, they move staff on in this unit pretty regularly, especially once they have kids, as the porn involving children is the worst (and they get years for making that, rather than months if it's just adults that are the participants). You are not allowed to work in the unit if you have kids under 16, as the temptation to go around with a shotgun has proved too much for some people in the past.
So there are people out there that are doing their best to stop this, but it's an awful job, and there are lots of safeguards to ensure the well being of the normal people who have to watch such awful things (psych evaluations, counselling etc), to make sure it doesn't impact the good guys too deeply.
America has the right idea for child molesters, either the chair, lethal injection, life meaning life, and chemical castration being some of the weapons in their arsenal.
I think that castration should be an option in the UK, for child molesters and violent rapists/murderers. Even if they are released, they physically wouldn't be able to do anything. And they should be fitted with a tracker for life, so you can keep a watch on them to make sure they don't try anything else.