Why do Porsches (and the ilk) send other drivers into rages??

[DarkStar]

Cruising home yesterday, I almost had to get out of my car at the red light and beat someone bloody. I'm driving normal behind a Jeep Cherokee with a ton of 2x4's on his roof. I'm not tailgating or honking or anything, I'm just cruising as I'm getting closer to home. Guy randomly looses his ****************, starts by sticking half his body out the window to flip me off, pointing at the **************** on his roof and then proceeds to start attempting to brake check me. I'm still a couple cars behind him..... But at one point he does slam on his brakes hard enough that I almost have to come to a complete stop. If I didn't get a phone call at this time, and had to turn, I would have done something. I'm usually the calmest person behind the wheel but when you start endangering peoples lives because your'e a crack head, I will break your jaw.

I don't get some people.