I already tried this on the SDMB sometime ago, but as I was busy trolling it at the time it wasn't considered properly, so let's try again, without the trolling.
My theory is that most internet paedophiles are actually rape fetishists. Permit me to explain my logic:
If one were a rape fetishist who wanted images of REAL rape, where would one find it on the internet? There are no websites (I should have thought) where rape pornography is openly distributed, but at the same time there are ones where child abuse is, presumably. What is one of the incidental properties of child abuse? It's rape!
So for the rape fetishist to find rape, all they need to do is find child abuse.
Now we've established that child abuse viewers might be rape fetishists instead, all we need do is think which is more common, and the best way to think about this is genetics; those who enjoy rape will be very successful at passing on their genes due to all the rape, while those who enjoy abusing kids will have less kids due to sleeping with the infertile, and possible abusing their own children. Therefore rape fetishists are by far the most common, and assuming a similar likelihood of seeking out the child abuse material, they make up the greatest numbers of most so-called paedophiles. QED.