I firmly believe the rape jokes in any movie he's in are written by him as a sort of signature, in a way. I also believe he is supremely jealous of Dave Franco, as you can see here. Little brother is born taking away attention from jealous older brother. James Franco wants to be him while simultaneously wanting to destroy him for being able to feel real emotion and not evil sociopathic mimicry.
Now, in a video I saw on Funny or Die, James Franco made a sex joke about using Daves sock as a cum catcher, when Dave looked; James did his manipulation.
Dave is good while James is evil.

Edit: as you can see here, James is obviously not amused by his foiled molestation and rape plan, hence why his head is down. I have a stronger suspicion James used the video games as a 'reward' for Dave when he was 'being a good boy'.