...you have to just let him do it or ask him to stop and risk confrontation to where the prosecutor says "...so and so shot so and so for checking his jug lines..." Even if the bad guy threatened you when you caught him...it won't matter.
So if you are carrying and some guy flips you off in traffic, and you CHOOSE to flip him off back, and it leads to him attacking, then you might not be off the hook if you shoot him because you chose to escalate while you were armed. Isn't that the way the law is setup?
Depending on the level of threat and assuming the perp has a weapon, you would be well within your right to defend yourself. It is my understand of the self defense law, that if you are legally allowed to be where you are at, you have no obligation to retreat.
And to address your last comment, I am not aware that if you return the middle finger to someone, that gives then rights to whoop your ass without you being able to defend yourself up to and including deadly force if you fear for your life.
Hopefully I will never have to defend myself in either one of those situations. But I can tell you this, dead men don't talk.