Don't get all bent. It happens and will continue to happen.
The best response is to point at them and laugh. Make sure they see it, and when they do they will get more enraged, and than laugh harder. F(_)ck em. Take out your phone cam. and take their picture all pissed off! Laugh again!
If they show an aggressive response where you "fear for you personal safety," than run their asses over!
Not a suggestion, but a fun way to deal with the tree huggers.