I know exactly how you feel. I work in a grocery store and we have several of those people we deal with frequently. There's one that is an absolute asshole to almost everyone that works there. I've only seen him be nice to about a half a dozen workers. The rest of us he treats like trash. However, he's always nice to other customers. I try to deal with it by telling myself that he must have such a pathetic life that he has to treat us "lowly" store employees like **** to bolster his own self esteem.