I see a lot of bad advice here. Most verbal confrontations are going to be well within the safety zone of using a firearm. Most attackers can cover 10 feet faster than you can draw, aim, and fire.
You need to be thinking about how to prevent the escalation, watching for signs of escalation, and positioning yourself to have the best advantage. If that means unbuttoning a jacket, putting your thumb in your shirt, or anything else that doesn't scream "I have a gun and will shoot you", then you do it.
Obviously you don't threaten, you attempt to de-escalate, and you try to get the attention of anyone who can help diffuse the situation before you decided to use force to defend yourself. But there is nothing wrong with positioning yourself to have an advantage should force be needed.
If someone was screaming at me, I'd make sure I'm standing, with my weapon side the furthest from the aggressor with good posture and balance. I'd attempt to keep as much distance as possible without aggressively fleeing, running, or moving in a way that would provoke. I would apologize, no matter if I did anything. I would speak loudly but not yelling to try to get others to the area. I would start to make mental notes of walls, obstacles and other things I may use to keep distance from the aggresor or that could be used to corner me. I would watch his shoulders, as they are always the first sign of an attack.I wou ld be prepared to move in a circular fashion, not just backwards or forwards. Finally I would probably bring my hands to my waist (hands on my hips like I'm resting them), to close the draw distance.
I personally would rather hear that someone decided to be prepared when someone was getting aggressive and it turn out it was not needed, then someone not be prepared when the aggressor escalates.