Talking about sex is a just another form of having sex and you should never feel like you’re being forced to have sex.
That said, you can’t really go to the cops about an uncomfortably sexual conversation. If he’s making you uncomfortable just tell him you don’t want to talk about this and if he doesn’t respect your wishes, then he doesn’t respect you and you should drop him.
If someone didn’t respect my wishes to keep conversational topics away from ugly and negative ones, I would not hesitate to walk away from them mid-sentence.