Might as well
Alternative sexualities are a fad rn
If it means people don't bother you about shit, then you might as well just say that. If the conversation continues, you can try to re-direct it towards talking about asexuality (since it's probably exotic to them), the rise of the asexual identity, or w/e with a bit of research. Normies are v open to that kind of conversation in the modern day, shit like 'I'm black, let me tell you about my experience of racism and what BLM means to me,' 'I'm a fag, let me tell you about how I came out and found a community,' that kind of shit. They're sort of expected to, due to wokeness.
No harm in talking random shit about asexuality, including some fake feminist talking-points if the normie is into that, stuff like, 'Idk society is really sexualized nowadays, they sexualize women and shit all the time, so asexuals find it kind of overwhelming. It's not that we're, like, Puritans, but it's like being bombarded with loud club music when you're not drunk, right?' etc. etc. Just some random BSing to get the conversation away from that subject.
Just hide your porn stash.