Agreed, If that was so, then women would not treat one another that way when there are zero men present/available. But many do.
Likewise, mothers, grandmothers, and aunts would never treat the younger females in their own families this way. But many do.
Cats and other mammals which typically have many females and only 1 or 2 breeding males around would likewise not treat one another competitively, since all are breeding with that male regardless - but, many do.
Think I’d have been happier if it had just been more honest and the title was, “Bitches! Why?” Then, you could probably actually sell an ironically misogynistic answer and cast all females in a single mold. Because (insert answer here)" response. Because hormones. Because tribe. Because bitches be. Or the present, because d***. (Who, but a guy, would even…?)
Now, please excuse me. I need to go suffer over my appearance, lest my single desire in life be unsuccessful and I earn criticism by others of my gender…8P