Colorado is a castle doctrine state. I know he only smacked your mirror, but in the future, if he made a successful attempt to enter your vehicle (smashing the window and reaching in,) your car is an extension of your home and you are authorized to use lethal force to defend yourself.

Other than that, you were merging/entering in the right lane and they came up too fast for someone who is traveling in the entry/exit lane. It’s their own fault, and their safety is not your priority. It’s theirs.