You must'a been on the East Coast?  People on the highway are MEAN! out east.  They'll do whatever they can to make the other guy inconvenienced or worse.

My transmission went out once in New Hampshire and I had to walk along the highway to an exit.  People would give me 'the finger', they'd throw bottles or anything they could find loose in their cars at me.  Some tried to run me down and I quickly learned to not be caught out in the open, but to stand behind road signs to avoid being run over. 

I guess it's just a lot of pent-up anxiety?  (And NO - I wasn't wearing a red cap!)