So many people don't take it to heart. "Do unto others as you would have them do unto you." If you wouldn't like to hear something about yourself, don't say it to someone else. If you wouldn't like something done to you, don't do it! But it seems this is impossible for some people to put into practice.
I've worked in retail since I was 18, and I could sure tell you some stories. People who want you to drop everything and focus on nothing but them, yet whatever you do is still not good enough. People who think that you're out to get them, personally, and cannot accept that when you say something is against policy or that the computer won't allow you to do that, you're not lying just to piss them off. And it's not just retail, either. A friend who works as a bank teller regularly hears from irate customers with empty bank accounts that she's been stealing their money and going shopping with it, and that's why they're broke.
I'm sure we've all had experiences like that, in or out of work. And then we spend the next two days telling anyone who will listen about the woman wouldn't say a civil word to you, but was extremely polite to your manager when you called her over, or the guy who screamed at you in the Wal-Mart parking lot because he almost ran into you! I think it's just human nature to repeat stories in order to remember them, internalize them, and receive feedback and validation for your feelings about the events. Sometimes you just need to hear, "Man, that sucks!" or "I'm so sorry, what a jerk!"
I don't know why people seem to have so little regard for others. Maybe, sometimes, that rude person is just having a bad day and feels sorry later for snapping at you. Maybe they just had a fight with their husband or daughter and took it out on you, and the rest of the time they're perfectly pleasant. Or maybe their parents just didn't teach them manners, and they inflict themselves upon everyone in such a way.
Which is still not an excuse. None of it, not having a bad day or a fight or a lack of good influences as a child, excuses rude behaviour. I think if everyone just thought "How would I feel if this happened to me?" before they said or did anything, and then applied that thought before they spoke or acted, there would be a lot less hurt feelings, anger, frustration, and sadness in the world. If I'm not careful, a run-in with a rude driver or an angry customer can ruin my whole day, even though I know , logically, that I'll never see them again or have to deal with them. And I don't think it's fair to do that to another human being, no matter your circumstances.
I know I'm not perfect either. I might be snippy to a customer service person if I think they're being condescending, or honk my horn when the guy ahead of me doesn't notice the light has changed. But especially after working in retail/service (and I'm sure everyone who has feels this way, too) I try to be considerate. Just because someone is in a position to serve/help me doesn't mean I should take advantage of them. I just wish everyone felt this way.
Now spill. I know you have some story you're dying to share!