That actually brings up another good point...
The idea that the bar owner was rude, so I'm walking out.
90% of the bar owners are Adam Henry's. People in the crowd will stumble their drunk asses up to the stage and berate you. Expect to be disappointed if you have expectations of being treated well.
The ego will cost you work. You walk out because he talked to you harshly, you are the one ending up with a reputation for being temperamental and being unreliable. "They walked out in the middle of a gig" is what the next bar owner will hear.
The same ego that tells you "I'm not going to turn down any further", or "He can't talk to me like that, I'm walking out" needs to be tamed. Learning to de-escalate these situations is pretty handy.
The way to turn that around is to be more professional. Be proactive, come back in a few songs, ask how the volume is. Get it under control, now you look like the adults in the confrontation, talk to him later, when you get paid. Now you can bring up, just let us know about the volume, no need to yell, etc, don't appreciate being talked to like that. And drop it, don't engage if he goes off on a rant. If it bothers you that much, don't book there again. But be the better man. Stick to facts, don't get personal.
Its like in the business world, you must try to avoid burning bridges. Word travels very fast. Bad word travels faster.
You tend to get defensive, get your hackles up. Nothing good will come of that. If he's a dick, doesn't realize he was wrong, is obnoxious, why should you care what he thinks. He is a dick. Be more nervous if he thinks you are birds of a feather.
The best revenge is playing at his competitor and drawing a crowd. That's how you win, not by getting in a pissing contest with an obnoxious bar owner.
Randy