You can criticise groups of arseholes based on their behaviour, not based on their membership in a class of people. We have plenty of insults that do that. So if we're not that different, why do we need an insult that ONLY applies to women?

Did you think about what I asked you to think about? Did you think about making an insult for a marginalised group? Can I help with some concrete examples? How about gay men, or disabled people? Would you feel comfortable creating an insult that ostensibly applies to bad behaviour from people in those groups, but which ONLY applies to people from those groups? Would you think it a good outcome if other people--people who hate or disrespect gay men and disabled people--started using the insult you created to refer to ALL gay men and ALL disabled people, regardless of whether they were displaying the behaviour the insult was intended to describe?

Karen may have started as an insult to describe entitled behaviour, but it will end as a general insult for women. So called progressives are loading up the word Karen with hatred and negativity, and those associations will still be stuck to that name when misogynists start using it to refer to women generally. If you doubt this, look at 'b*tch'. It's ostensibly for women who are aggressive arseholes... and now men use it to describe women who disagree with them, women who refuse to have sex with them, all women, any women, every woman.

To say that white, middle class women are not marginalised is to say that sexism doesn't exist, or that it only exists when women are marginalised along another axis, like race or poverty, that is also experienced by men. Catharine McKinnon has a paper on just this, if you're interested.