"He got teased for being fat". I got teased all the time, why is being teased about being fat any different/special?"
I.e. I'm not saying it's "okay" to tease someone just because I question why being teased about being "fat" is any different to other kinds of teasing.
It just is. It doesn't mean that vapid reasons are not vapid, but this isn't vapid, it's toxic.
I don't know what other kinds of vapid reasons the parent was referring to, but many are just as bad as "female". There's the obvious ones: racist, homophobic and transphobic justification for example, but also less common, also harmful vapid justifications. Dismissing someone's idea because theyre an ex-convict is a good example. Or on the basis of their age.
These are all quite bad, even if not completely equally so. I'd humor an argument that "female" is the worst of these simply because there are a lot more women than ex-convicts and members of a gender or sexuality minority, and therefore more people who could potentially be hurt.
But not "it just is".
Why should a reason of "female" be special?