So how young are the girls OP is upset about not accepting his friend request? If there’s concern that some people would refer to them as “girls” instead of “young women” the grossness of the statement stands.

I don't know & neither do you: the words are vague as you likely know. A sensible interpretation: they're discussing girls who could be young women & vice versa.

They didn't say they were upset.

If there’s concern that some people would refer to them as “girls” instead of “young women” the grossness of the statement stands.

Not really, and still not answering the question: you do that an awful lot.

You've never encountered older women who want to be called girls or girls who want to be called women or people sensitive about their age who find the wrong word offensive? They averted that minefield.

You go on this long when people make grammatical errors like using the wrong “their” in their posts? Or is it just excusing language the dehumanizes women that gets you fired up?

You're digressing & excusing treating females like a dirty, toxic word by nitpicking any mention of it. I'm not here (1) pretending the use of females is offensive, (2) failing to properly articulate how the problem isn't the word when (3) we all can see the context isn't offensive.

The question remains: what good does that advance? I understand why misogynists would want you to keep promoting their usage of that word: if everyone stigmatizes the noun female, then it becomes generally accepted as a dirty, toxic word, so yay misogyny.

Nonetheless, they're the minority, and the common usage of noun female isn't offensive until we change it.

Anytime someone says “can’t use females anymore, misogynists use it” instead of resisting that by reasserting the more common usage, they’re letting a minority like those misogynists take over & decide the meaning of language for the majority. (Unwitting) accomplices take capitulation a step further by policing language to promote & enforce misogynist meanings: regardless of intent, that's you.

Language & cultural conventions take cooperation: stop cooperating with & caving to misogynists. Definitely stop actively supporting them.

If you're going to advocate for a cause, then stop incompetently betraying it. Your cause deserves better than incompetent advocates like you. So tell us: what good is that language policing advancing?