As a cop, here is my advice:

Don't yell at motorists. Road rage works both ways, and you could be yelling at someone who is mentally imbalanced and has a gun in the car. If you are concerned enough at the guys parking job (parking on the wrong side of the road is illegal, parking on the sidewalk is illegal) to consider it a safety issue, get a LP and call it in to the non emergency number. Once the guy yelled that at you, I would have certainly called. The police may not have been able to do anything about that except perhaps disorderly conduct (maaaaybe), anyone who is squirrely like that generally will get squirrely with the police. NOT a good idea.

Now, have I yelled? Yep. Shaken my fist? Yep. And, on one occasion, when a guy with a boat deliberately tried to hit me (I was going 24 mph on my bike in a 30 mph zone...not fast enough for him) I badged him (I had it in my wallet, which was in my bento box) when I caught him at a light. I was out of my jurisdiction or I would have detained him...as it was I gave him a fright. Dumb kid. But I would NOT recommend ANY of those actions.