To me, the only time it is ok to hang up on a person you know is if they are screaming at you down the phone and you need to cut the call short for your own (mental) protection.
So how come with some people it happens in a normal quiet conversation? Hanging up on someone is rude, obviously, but more than that, it is passive-aggressive behaviour in order to win, despite not having a cogent argument.
It is the ultimate form of dismissal of who you are and what you have to say, usually by someone who is incapable of rational discussion.
Not that I don’t FEEL like hanging up on people from time to time, it is just that it is such an admission of inadequacy that I don’t do ever want to be guilty of doing it.