Looks like you've got some solid encouragement/empathy already but here's my two cents anyway.

You shouldn't need to create a rape scene to add drama to your story. Illithids exist. Wendigos exist. Nightmarish creatures of flesh, teeth, and tentacles exist. Even if you as a PC don't roleplay fearfully enough for your DM, there's the fear status debuff which can force your PC to be scared. So there is no need for a rape scene.

Above that though, it's irresponsible to include that content. You have to remember you're a group of real people with real lives sitting at a table together. It's possible someone has had first or second hand experience with rape and isn't in a position to roleplay it during a leisure activity.

I don't know your DM, it's possible they aren't a complete piece of shit, perhaps they are just naive to the possibility that someone at their table could have a real problem with rape content. Maybe they are too caught up in the opportunity to capitalise on your character's weakened state. Maybe they don't understand that just because the game isn't real doesn't mean that people can't be upset by it's content.

I'm not sure how being uncomfortable with rape is childish and immature. I'm an adult and rape disturbs me. It's fucking terrible.

If you need a new group check out mythweavers or use the subreddit links to the LFG in the sidebar.