This can work against him. They can go to other players in the area, tell them "Kevin Video's into some sick shit, he had our characters get raped in his game as a personal vendetta!"
Wouldn't be the first time my name would be mud in the gaming community as a DM. The only problem I'd have in the end is that two of my players also game on Fridays as well. Could be a bit of hostility in that, but I'd think they'd be mature enough not to do anything childish like holding a grudge.
Right. No. These players have shown, as far as I have seen, that they are EXACTLY the sort of players to hold grudges. Either way, though, the game needs to be brought under control. I agree with laying all your cards on the table - and if you're not okay with playing an evil game (and most new DM's really shouldn't touch anything like that) then tell them that. Period. Stop. End of conversation. They are welcome to play with you on the condition that they play the game that YOU want to play too. The game is supposed to be fun for everyone, not just the DM.
And, for what it's worth, if ANY players in ANY of my games (except an evil or other game where such things had ALREADY BEEN AGREED TO at the BEGINNING of the game) tried to pull this - especially rape - well, I'd go completely bonkers and apeshit on them. Not cool. Maybe what you need to have with them is a discussion about consent, consensual sex, and how rape =/= cool. And, in fact, how rape often leads to things like revenge, or being assaulted by
The Most Prepared Woman in the World (trigger warning for attempted rape and "taking aholt"). Oh, and then there's prison.