I agree, but I also think that applies to the celebrity as well. Ive heard some absolute horror stories about people that have met celebrities in public, and while you can debate the merit of approaching them for an autograph/picture, the famous person is extremely rude to the point of cruelty. The usual response to this is "maybe they were just having a bad day". As if that is any real excuse for that kind of behavior.
I have a lot of bad days too. Wouldn't make me any less of a raging a-hole if I unloaded on strangers, regardless of if I found them annoying or not.