I don't think this is a good analogy. There's strong evidence that drink driving increases the risk of accidents, which is why it's illegal. Child porn is illegal because children are harmed to make it. It's _possible_ that the existence of child porn increases the chance of a pedophile acting on their urges, but if there is I don't know of any studies. An analogous (and more ethical) study might be whether or not people have more sex in places where pornography is easily accessible, but I have my doubts. It's well documented that young people are having less sex in general than previous generations and porn is more accessible than it's ever been, so if anything it appears the correlation might go the other way.
EDIT: I think the other far more compelling argument is that allowing any child sex images to exist at all normalizes it, and could make people consider it less harmful. Could it increase the rates in which people who are otherwise not pedophiles abuse children? I don't know the answer but it seems like a question worth asking.
Yeah it is disgusting, but who is suffering or being molested or abused here?