"You either do or don't support rape, there's no ifs ands or buts."
This mindset is wrong since a lot if not most people who enjoy rape porn don't support rape in real life. Who would've guessed? Since people have different standards between fiction and reality the line isn't as black and white as you say it is. However do note that there are people who can't stand rape even in fiction and OP's message does serve as a good warning to others like him.
I do agree with you saying that rape isn't okay just since you're raping an evil person. 'Giving them a taste of their own medicine' is a flawed mindset at best. Killing an unrepentant murderer is fine with me as it removes the risk they pose to other people, but raping that murderer achieves nothing but dehumanising them, which has no substantial benefits that I can think of. (This is just an example, I haven't *yet* played the game)
Also, OP: dropping a game for "implied rape that might happen" is... hasty and rash. Though you do you I guess. Not like I can realistically stop you from dropping support for a game that has kinks you aren't okay with.