Don't ever let things like this bother you. Same thing when people cut you off on the highway. They're not upset about what they did, why let it get to you? They did something wrong, you being the one upset doesn't make much sense.

I always feel sorry for people like this. No, really. I look at this way: "I'll wake up tomorrow and not have to deal with you. You'll wake up and still be an idiot!"