You say, “So their bitchy attitude was defensive.” Perhaps, but over-confidence, an awareness of one’s primal power over others, is probably at work in many cases. A bikini is an act of aggression in its own way. I realize many girls don’t mean it that way.

"Persistent behavior becomes habit or second nature. The emotional hardening that began on the beach in scanty followed many girls whom I knew into their twenties and beyond into their adult lives."

True. Immodesty makes women mean and callous.