There are two kinds of men that are relevant when talking about causation here:
- Those that do not rape as long as they can buy sex.
- Those that do rape when they can buy sex.
In my humble opinion, it is rather likely that there are more in the former than in the latter category, thus I would think that causation is plausible here.
On the "something doesn't quite feel right" thing - do you have an emotional reaction to this topic?