In my opinion CSAM is a symptom, not a cause.
It's difficult to "stumble across" that kind of material unless you're already actively looking for it, which means some amount of "damage" is already done.
I also highly doubt that someone with no proclivities in that direction would 'turn' as a result of stumbling across CSAM. I'd guess they'd go the other way and be increasingly horrified by it.
