I am queer. Somewhere between bi and ace, haven't exactly pinned down exactly where but I definitely claim both labels because I feel they both describe me. I'm part of a community of mostly queer people in a show's fandom, and we pretty much ALL have our "your fave is queer" headcanons.
For me, my first exposure to the idea of asexuality in this context was through fanfic. Reading the fic, especially the ones that were explicitly about Being Ace and What It's Like For Ace Characters In Relationships, helped me understand a lot of things about myself. That got me researching specific terms I encountered and interacting with people with similar headcanons, and finding the words and explanations for myself and how I feel.
As long as people keep in mind that their headcanons are not the same as Actual Canon, I think it does more good than harm. I can understand, given the irresponsible speculation that hurt you, why you disagree.