I guess I've never looked at it as "an issue." I think there are plenty of ways to approach sexual conversations without being gross or distasteful. Besides, if folks are gonna bring up a topic, then they should be prepared to get responses.

Nevertheless, if such conversation makes you uncomfortable and you don't want to "out" yourself, yet you still have the urge to correct, you can always try taking the erotic aspect out of it and throw out purely medical facts like you did in the paragraph above where you mentioned anal and fisting. That's not gross, just basic biology. You don't have to mention it doesn't hurt you or that you like it - just the facts, ma'am, as they say.

Just remember that there's a big difference between a misconception and a preference - asphyxiation or anal or whatever doesn't turn everyone on, even within the kink community. Just because someone isn't interested themselves doesn't mean that's because they just don't know better and haven't tried it yet.