Poor Mocha, I'm sure his world was all shook up by the arrival of the kitten. I'm sure he's trying to figure out just what his position is as far as dominance goes now that the kitten is in the picture. It's important that you let him know you are still boss.

Perhaps the bath issue is associated in his mind with the kitten or it could just be a time when he feels he can act up cause he has your attention and the more he fusses about the combing the more you try to comb him, the more attention he gets - is that what happens?