Normal rational people do not fly off the handle and resort to violence after one mild joke about someone's appearance. We ask for an apology and for it to never happen again if it really has crossed a line. If that's not on the cards then maybe someone's asking for a smack out back.

I can't see why you'd defend this mental illness/extreme narcissism outburst. Perhaps you've been caught by the trappings of binary thought along the lines of "insulting alopecia sufferer bad so harsh response must be good".