Ask your players' permission before you do something to their characters. Not even talking about sexual violence here. You can and should do it with physical combat violence too.

Make this part of your gaming lexicon:

"You're going to take 6 damage from this attack. Can you tell us what that looks like?"

Give the player the license to describe what happens to their own character, in as much or as little detail as they're comfortable with.

Because if it's combat, you don't always have the option to say "No that doesn't happen." But you do have the option to say "I'm not going to narrate it."

I'm using combat violence as an example here because it's the thing from D&D that a lot of people take for granted as being "just part of the game" that the GM gets to decide, but it very much doesn't have to be.

And if you don't let it be that way for combat damage, it's easier, a lot easier, to not let it be that way for other kinds of character impacts.

"I think what happens here is, the mechanic wants to try and give you a sexual experience. How do you feel about that? Do you want to play out what happens, do you want to let it happen off screen, or do you not even let it get that far?"

That does two things.

First, it gives the player a chance to say no, and to dictate the terms of what's happening to their character.

Second, it gives YOU AS THE GM a chance to say no to yourself, to really think about if this is a story you want to tell.

Give yourself an out. Give your players an out. Let the players say no. Let them know they're allowed to say no.

Do it with the easy stuff. It will make it easier to do when it comes to the hard stuff too.