Though poorly executed, I think the Spock observation to Rand was meant to point out what makes Kirk (or any man) an "attractive" male, not about enjoying sexual assault. Couple the two Spock dialogs together and I think this makes sense:
and lastly,SPOCK: Judging from my observations, Captain, you're rapidly losing the power of decision.
MCCOY: You have a point, Spock?
SPOCK: Yes, always, Doctor. We have here an unusual opportunity to appraise the human mind, or to examine, in Earth terms, the roles of good and evil in a man. His negative side, which you call hostility, lust, violence, and his positive side, which Earth people express as compassion, love, tenderness.
MCCOY: It's the Captain's guts you're analysing. Are you of that, Spock?
SPOCK: Yes, and what is it that makes one man an exceptional leader? We see indications that it's his negative side which makes him strong, that his evil side, if you will, properly controlled and disciplined, is vital to his strength. Your negative side removed from you, the power of command begins to elude you.
SPOCK: The, er, impostor had some interesting qualities, wouldn't you say, Yeoman?