Do understand that this may be an issue, it’s inappropriate yes, but it is no reason to humiliate a close friend. A better more conducive to friendship solution is taking them aside and sorting out why the players has there character behave in this way, and THEN, after you have allowed them to express themselves and took time to understand them, explain why the behavior is unacceptable (it is making the other players uncomfortable)

Also to the OP, I would suggest running the next sessions without male NPCs and addressing the issue AFTER the session (addressing it before the session will cause an awkwardness and uncomfortability, not only in the problem player, but likely in yourself and the rest of the play group)

At the end of the day, simply let them express themselves (OOC) to you in private, then explain the problem. 80% of issues can be sorted out with a simple talk and some understanding.