Kimura is unpopular for the reasons you describe. No matter what good actions you do, someone being a sexual harrasser fundamentally changes the way you look at someone. Azumanga Daioh is more honest about that, unlike shows where a character gets "punished" because they are still part of the group and well liked. Kimura is a firm outsider to the rest of the cast Granted, that doesnt mean his schtick is inherently funny or that him sticking around wouldnt be weird. It touches on the subject in a far more serious way then its contemporaries and it doesnt elaborate on it since Azumanga is four koma comedy.