This is the shitty part, due to the actions of assholes (blocking the road), people are at the mercy of the prosecutor. Do they want to make a name for themselves, or do they support0 antifa/blm? All we can do is mentally prepare for as many "what if's" as possible.
Since this happened in OR, I will expect charges to be filed on the driver. OR prosecuted a camera man who drew his gun when a group of people started to approach him and yell at him. He got 5 years IIRC.
People in CCW states are arrested often for drawing a weapon. Without a witness or video to corroborate your story, there's no way to prove you were in fear for your life short of pulling the trigger. Using the gun to scare away a would-be attacker is a crime -- not just brandishing, but may be aggravated assault with a deadly weapon.
One method is call 911, leave the line open, and then warn the attacker to stay where they are - that you are armed and will shoot them if they come any closer.
Another is to leave the firearm holstered, don't tell the attacker you are armed, and try to deescalate the situation. Threatening to shoot someone often has the opposite affect -- they might see it as a challenge, not a warning to be heeded. Wait until you feel there is a perceivable threat to your life, then draw AND FIRE. Theoretically, you should never draw a weapon in public unless you intend to shoot. If the shot misses and the threat runs away as fast as his sagging pants allow, stop firing. It's a simple test: if you felt threatened enough to draw your firearm, why did you not feel threatened enough to pull the trigger?
Easier said than done. Once you have that sight on a breathing human being, it's often very difficult to follow through and fire. If you hesitate and the person leaves, tell the Cops that the presentation of your weapon was sufficient to stop the threat. Don't tell the Cops you tried to scare them away.
In fact, don't tell the Cops ANYTHING other than you'd like your lawyer present before giving any statements -- then shut the hell up! If you didn't injure or kill anyone, the worst thing you can do is explain your actions under duress at the scene.