Rude behavior

I drive a Dodge Challenger with the 5.7L Hemi. One of the first things that I did when I bought the car was to have the exhaust straight piped. This makes the car fairly loud, and for this reason, people often think the car is going faster than it is.
Periodically, I have people (always women) yell at me to slow down. The conversation usually goes like this:

Woman: "You should slow down. The speed limit here is X."
Me: "How fast do you think I was going?"
Her: "Too fast."
Me: "Are you a cop?"
Her: "You need to slow down."
Me: "Go fuck yourself."

I have been told that I am being rude. I agree. However, when another person appoints themselves as the monitor of my behavior, my attitude of "you're not the boss of me" kicks in, and I tell them to stop. While rude, I don't think it is out of line.
The stopping distance of my car from 30 mph is 23 feet. The stopping distance for a minivan from 20 mph? 25 feet. Why? Because I have
Anyway, just who appointed you to be the traffic monitor?