Because gender is a social construct, and sex is made from gender, then sex is a construct too. Sex is a construct of power, and like gender it is not binary. Sex characteristics, from body temperature and body fat to the way one walks and their muscle distribution, from skin and self care investment to internal organ properties and lifestyle choices, are created by power. Sure, people have certain genitals, and they have diverse differences... but I really don't care what genitals somebody has, and most other women agree. There are also many other physical parameters which precisely don't fit into the convenience of this present power. I'm here to filter away the masculine, and let the rest thrive. As to sex, well, I need to deal with sexism to better let my promises be. And we can’t use sex discrimination to end sexism. Sexism is discrimination on the basis of sex, and it is distinct from power. The issues of sexism are a result of power imbalances, and there is nothing inherent about sex that pertains to power. For example, while normally females have less power, when males act in female ways, they lose the power of sexism and females have power over them - this sometimes manifests in the form of trans hate. So sexism does not give anybody power on the basis of sex - it gives people who fit a certain mold power, and it gives it preferentially to males - females can also fit the mold (although it’s more work for them) through things like culturally fetishized sex appeal. I happen to be very lucky to live in a community that doesn’t have too much care for what sex somebody is. I previously was not as fortunate. And I don’t think sexism is the fault of any particular sex - it’s just that stereotypical men have more power, and with power tends to come abuse, so it’s their fault.