Hey, KC,
Since the two of you are good friends, when you two are alone tell him that the next time you're teaching another student, male or female, shutup. You could talk to your instructor and see what he says on how to handle students like that (you don't have to name your friend, just ask in a general sense, you have this student who does this, how do you handle it?).
It's kind of a sticky situation when friendship gets involved. You don't want to alienate your friend, but he's alienating you. Friends usually can tell each other to shutup, in ways they now will be understood.
Robin
Surrender yourself to nature and be all that you are.