Awful behavior but I wouldn't give it further thought after leaving the airplane. Stuff happens and there are more important people and matters to bother about in life. OP Jim is not worth your energy or bother.

I don't see that writing UA will change him or others like him as such behaviour will not surprise anyone at UA - as stated this is more a cultural or systematic problem with UA rather than an individual bad egg. I can't even picture any FA on ANA or Thai, for example, behaving in such a way - even if they were having the worst day of the year.