You know, I am often told that I am rude or callous. I think it's just that people don't like my "happy-go-fuck-yourself" disposition. I can't possibly please everybody so I cut my losses and refuse to please anyone.
He might have been having a bad day or something too. Also, everybody's brains are wired differently. Perhaps he doesn't believe he has to return smiles (you really don't if you don't want to). Not everybody is going to fit your definition of polite. To be honest, that's not that rude at all. What would be rude is if he said "piss off" or something
I don't really get that much here... probably because I live in a small town in Rural Ireland and everyone tends to be as friendly as fuck. If they don't say hello to you in the street, they're probably not Irish. =B