If viewing an image of child abuse is wrong. Isn't viewing an image of ISIS beheading someone also wrong? In both cases the crimes were committed and the images produced to satisfy an audience. But one is illegal because it's perverted while the other is legal because presumably far more people have blood-lust than a minority sexuality.
In Australia it's especially bad, with somebody being convicted for possessing hand-drawn Simpsons porn. There might be a copyright case there, but it's hard to make the connection between that activity and actual harm to any children. The defense argued that they weren't humans because they had 4 fingers and misshapen faces. This kind of case is what happens when the "evil pedophile" mindset overwhelms people.
http://www.smh.com.au/national/simpsons-cartoon-ripoff-is-ch...
You could go a step further and ask what's the difference between a parent taking photos of their naked child playing in the bath, and somebody doing the same thing but then having a wank with the photo later? I think the difference is that one is "normal" and the other is "perverted", so we make one legal and the other illegal. I probably appear in some baby bath photos and I certainly wasn't scarred by it. If they got onto the internet and people got some pleasure from them, is that really going to scar me for life, assuming I even know about it?