I wouldn't call that rank sexism, there was no implication that Kirk would misuse his position, or that Rand was in any way inferior to male yeomen. If Kirk was tempted, well, he actually did keep his hands off the women under his command.
Not that I'd call Trek a model of equality between the sexes, not when 90% of the women in Starfleet are 20-year old hotties with low-ranking jobs. No, 90% of the Galaxy was populated by hot babes who only existed to fall madly in love with Kirk. And that's why Uhura is still so beloved, she may have been a hot babe but she was someone you could take seriously, and she never fell madly in love with a superior officer.