She humiliated him, and herself, when she openly cheated on him. There used to be not many things more humilititing than getting caught cheating on your spouse much less bragging about it.
Somebody joking about your medical situation isn’t humilititing to you, but it is very tacky and certainly not funny.
It might be very humiliating to a woman to lose her hair - or to a husband who has watched her go through that. (There are plenty of married people who have chosen to go their own ways while remaining married for various reasons. I may not approve of every case or in publicizing it; but in many instances they still retain a lot of affection for one another.)
She’s talked about her hair loss publicly for a long time. I’m sure most women would find it as devastating as she did.
To her credit, most women would probably wear a wig; but she just owns it.
And you’re correct - it was tacky and not funny.