That would probably more likely get you a polite correction on that type of forum. Partly because it's kind of a niche argument but mostly because it only invalidates the beliefs of the women who want to be men, who are often sidelined by their own ideological movement in favor of the men who want to be women.

By contrast, if you wanted to express some other truths that pertain to the latter group, such as "'trans women' are not actually women, they are men who desire to be women" or "there are a significant number of 'trans women' who 'identify' as women because they are men with a sissy porn fetish", then all their fury will be unleashed upon you. Even if you back it up with evidence and solid argument.