To be honest, that probably wasn't the best way to react...but it's hard to hold your tongue when some idiot nearly backs into you with his car. =/
If it makes you feel any better, I got fired from my job prior to this one because I swore to myself under my breath and one of my coworkers THOUGHT I swore at her, so I was fired on the spot without a chance to defend myself or explain that I wasn't even talking to that coworker. (Beyond that, people swear at each other there all the time and no one cares...but I wasn't one of the people that did drugs with the boss on weekends, so I didn't get the free pass others did.)
& it sounds bad, but you're better off at another job that you won't hate as much. :/