Even if you're against trans people, in an online forum, normalizing calling out pronouns allows cisgendered women to say "I'm a woman and would like to be called as such" without it being disruptive or cause men to view her as pushy.
All the more reason to explicitly call it out ahead of time, so they can be certain to use the right ones. Why would it be pushy, -especially- if there's reason to believe someone will use the wrong ones?
Really, I don't understand the objection; we pre-emptively give our names to people, for all the same reasons we might give people our pronouns.
