...I was thinking of the "spores" influence and Capt. Kirk's little jab about having the gall to make love to that girl.
Which reflects how language has evolved since the '60s. At the time, and going back to the 19th century, "making love" had a broader meaning than it does today; it could
be used as a euphemism for sex, but it referred more broadly to the overall process of courting and romancing someone -- even just flirting with or sweet-talking someone. (Cf. Danny Kaye's The Court Jester
, for example.) You often hear characters in old TV shows and movies talk about "making love" even when any mention of sex was absolutely banned by the censors (for instance, in I Love Lucy
, where they weren't even allowed to say the word "pregnant").
So Kirk's line wasn't meant to indicate that Spock had had sex with Leila -- there's no way NBC's censors would've allowed such an assertion to get on the air. It just meant that he was being generally romantic and affectionate toward her.