Had it done to me once by ex-boyfriend, years ago. I punched him in the face and he ended up on his ass, as the punch was unexpected. It was instinctive, I didn't plan it, but I'm not sorry at all. Dumped him after.
I'm a prude (and don't care it's supposedly 'embarrassing') and not okay with public nudity. I don't sunbathe topless, don't wear shorts with my ass hanging out, don't wear thong bikinis, scrunch bum leggings, super short shirts or massive cleavages, don't walk around my family members or partner stark naked and don't change in front of people. I don't care what other people do/wear, it's strictly personal. I'm perfectly happy how I am and don't plan to change in any way.
Therefore, such 'jokes' are a dumpable offense to me. It's not remotely funny, it's disrespectful, shows immaturity and contempt. Alcohol has nothing to do with anything, I drink myself, but I never felt the need to yank someone's trousers down to expose their dick&balls. If I can manage not to do that, so can men.