I also think Riker was in the wro
He was certainly the greater womaniser compared to Kirk
THe only time where I felt Kirk crossed the line of professionality is with the female Robot Rayna where they are seeking substance to create a cure for rigelian fever. Then Kirk then seduce the Rayna the ward/daughter of Flint who he is relying on in reliving the cure.
THe only mitigating factor is that Kirk actually falled in love nad it wasn’t a case of him sleeping around. The episode acknowledge Kirk was being unreasonable by having Spock called out on his behaviour.
I think there was another episode in the Roman Empire planet. Where the leader villain ordered a sex slave to Kirk and Kirk slept with her. Although then again maybe I can head canon that she was a prostitute and not a sex slave and hence Kirk is ok.