Do you believe that someone who plays a rape fantasy game is less likely to commit sexual assault than a person who doesn't?
I do not believe the typical person that commits sexual assault is a typical video game player to begin with. But as it is with any crime and popular hobbies you will find an overlap. But cause and effect do not even go into that overlap. Video games are no longer only for nerds.
You are engaging in the same faulty arguments that are around for decades to bash video games and the people who play them.
By playing a rape/sexual assault fantasy game (or, in other words, fantasizing committing about rape/sexual assault)
This is a fallacy.
So you accuse me of fantasizing of being a real life mass murderer when I play some first person shooter or basically any role playing game where you collect experience by killing?! Because that is what your logic boils down to. You assert that people who play such games fantasize about doing those things in real life. And from this premise you construct your argument how bad those games are. It is fallacious. Your premise is wrong.
If you want to argue soundly, try finding statistics that would link a rise in certain crimes with the popularity of certain games. But even if there is a link, the question is, what is cause and what is effect. A high unemployment rate can be cause for both - people having time to play games and people doing bad things.
Since a crime like sexual assault was done long before games and is still done in areas not known for their video game culture or freely available adult games, it is highly doubtable that there is a causal connection.
There is of course a cultural bias, but Japan is infamous for their adult games including questionable topics. And what do the statistics say about them? They have one of the lowest sa statistics worldwide. Some people even argue the opposite cause and effect and claim that this fantasy outlet reduces such crimes.
My stance is, that people can distinguish between fiction and reality. It is one of the first things we learn as infants. Pretend play. And they engage in fiction for entertainment, and not to fantasize about doing that fiction thing in real life.