Just say that you want Billy/Flint because you like both characters, not because it's important for social justice, or else you beg for the follow up question "so if Flint/another male character" gets to be canon instead, you'd be fine with it as well?

Oh, but if anyone on tumblr admitted this, they would have to come off their moral high horse and concede that most reasons for liking a show, ship or character are at best a mix of interest in social relevance of the material and emotional investment in specific narratives and tropes. Most of them aren't that self-aware. (And yes, there is the question why one doesn't leave; alas, since Teen Wolf fandom skewers young, most of the "discussion" actually happens there.)