The thing is, the 'geek girl' stereotype is something that almost never happens, but as far as I understand it the stereotypical hipster is not uncommon.
It is possible to 'like' something the wrong way: namely where you do not actually like it. Hipster hate isn't about being different, it's about a perception of dishonest attention-seeking.
Isn't this the same justification that's used to shame the "pseudo" geek girls?
As far as I am aware, the discussion of 'fake geek girls' has mostly come from MRA-types that spend most of their time failing to see women as people. So any particular instance of 'fake geek girl' is almost certainly the commenter being an ass and wrong. But, again, as far as I am aware, there are no large groups going around being 'anti-hipster' in situations where it doesn't fit. So instances of being 'anti-hipster' are often accurate.