I cannot think of anything worse than someone having Child porn
Certainly actually molesting the child is worse than having a video of that act.
I've got a bullet-proof vest for you here. I'm going to start shooting at you whether you put it on or not. It's not guaranteed to save you (I may hit you in the head), but it's up to you.
Personally, I'd rather take the potential immunity (even if it's only an 80% chance) than go completely without