First, make it clear that you don't want to engage in such a conversation. You can use humor to defuse the situation a bit, like 'Whoa, that's way too much information! Let's talk about something else, like that new movie we were thinking of seeing.' This way, you're gently redirecting the conversation to a more suitable topic without making your friend feel too bad.
Politely stop them and say that this is a very private matter and not suitable for sharing. For example, you could say 'I don't think this is appropriate to talk about.'
Tell them firmly that this is not an appropriate topic to share and that it makes you uncomfortable.
Politely stop them. Just say that this is an inappropriate topic and you don't want to hear it.
In general, these kinds of stories are not appropriate to share widely. Such topics are private and sexual in nature. Sharing them can make others uncomfortable and violate social norms of propriety.
I don't think it's appropriate to share such a story as it involves vulgar and inappropriate content.
Tell them firmly that you don't want to hear it. It's inappropriate and unethical.
You can start by showing interest. Say something like 'That sounds really interesting, tell me more!'.
Politely tell them that this is not an appropriate topic for discussion.
If someone mentions such inappropriate content in public, we should firmly and immediately stop them. We can say that this is not acceptable in a public or any civilized setting.
Politely tell them that this is not an appropriate topic for conversation.