You acknowledged them which was great, and then immediately turned around and started re-educating them. It was a valuable message to get out into the world, but a victim recounting their experiences is NOT the audience you should be trying to educate.
Just say “I’m sorry that happened to you, some people are scumbags, being cis is totally fine” and redouble your zeal to spread that message in a more appropriate setting.
Edit: To clarify, I’m not saying I doubt your intentions. What I am saying is that it wasn’t very tactful or self-aware.
Also:
pointing out that it’s not universal or even the norm
That’s called “denying someone else’s experience.” Again, it’s about the worst way you can possibly comfort someone who is talking about when they were hurt. It doesn’t matter if you think it’s common: it happened to them. Even if they were the only person in the world that had happened to, knowing that wouldn’t make them feel better.
I like to imagine this as just a shitpost tool where you can just paste any text anyone types to get a screenshot like this and instantly invalidate their argument
Or maybe that’s what this already is and I just WHOOSHed myself