I'm honestly not sure what seems ridiculous to you. In these instances, the female bullies are acting out misogynistic discourses. Can you clarify what your sticking point is?
And what do you call it when boys bully each other to enforce arbitrary social norms? Because I don't see a substantial difference between the two cases.
If you accept that our society suppresses women, it's pretty obvious what the difference is. One type of behavior directly reinforces the status quo, the other doesn't.[1]
And if you want to talk about societal problems, that's pretty bloody important! Yeah, both types of bullying feel just as shitty to the individual, but the broader ramifications are definitely different. Nothing is isolated.
If you disagree with the fundamental premise (society is sexist) that's a whole other issue, but you should be at least able to see why others see a distinction.
1. Keeping in mind that you seem to want to compare arbitrary bullying to the more specific type persimmons references.
It still doesn't follow from the premise that "society suppresses women to the benefit of men" that "any time an individual woman is suppressed, it is to the benefit of men". How do men even benefit from social taboos enforced my women against other women being geeky, or for that matter, slutty? That's probably the opposite of what would benefit men.
Society is more complicated than that. There are more forces swirling around than patriarchy. Any insular group will eventually enforce arbitrary social norms on each other, and since people tend to socialize with those of the same sex, both genders form insular groups in our society.
No, they are not "acting out misogynistic discourses", they are being horrible people. And let's be clear that it is no fault at all of men.
By the way, "sexual policing" comes from sexual competition and evolutionary psychology, which comes from thinking with your ovaries instead of your brain. In much the same way idiot men's one-upmanship comes from thinking with the testicles.
The fact that people act out larger, structural systems of misogyny doesn't exonerate them. A person still has agency, and to say that they are acting out something that is part of a larger discourse doesn't mean that they are helpless puppets. Another thing to realize when talking about misogyny and structural injustice is that it isn't blaming any given individual - that's what makes it structural. It isn't a cabal of evil men with a maniacal plan forcing women down or a statement that all men are bad and oppressive, it's a deeply rooted system of oppression that lots of people propagate, knowingly or not, through stereotypes, legal injustice, inactivity, social policing, et cetera.
And I think you are too quick to write off people's actions as evolutionarily programmed - it's a somewhat ironic response, given your first complaint. Whether or not there is a biological instinct to compete sexually, the expression of that instinct is a product of social norms. Arguments for evolutionary psychology have a troublesome and pretty untenable tendency to ascribe a complex, culturally-specific, and socially enforced behavior to some magical mystery determinism gene. It's kind of a pet peeve of mine.
Does it always bother you when people give uselessly reductive, empirically unsubstantiated pat explanations for incredibly complicated social behaviors, or only when they conflict with your own?