Last band I was in, the guitarist kind of held sway.
He was royally rude to the organiser of a charity event we played at.
After we played, I went over to said organiser whilst the guitarist was talking to them, apologized for his behaviour, and quit right there and then. The drummer was there, too, and quit as well, for the same reason.
Not exactly professional, but I wasn't discourteous. Nor was the drummer.