rude people

I have just been accused of having an attitude. Do I? I don't know. maybe I do. I didn't think I was rude, though. I wasn't trying to have an attitude. a student asked if he really had to fill out a registration form to only take one class--couldn't I just do it on the computer. I said no. he needed to fill out the registration form, which I pointed out to him, and said that regardless of how many classes or what classes were being taken, you still had to fill out the form. I also mentioned that he had to have his advisor sign the form (something you're required to do every time--since the guy is student teaching as an undergrad, I'd figure he'd have the rules down by now.). He said, but I did that before. I said (at apparently a bad attempt at flippancy/ humor), there's a first time for everything. he wigged out on me, told me I was rude and had a bad attitude. I said sorry. He said, are you serious???? I asked if there was something else he would like. He started ranting about how I was behaving, and then said, "I'm not going to try to teach you how to have manners." and stormed out of the office.
this is why I love my job. I miss retail. at least there my manager is the one who gets yelled at, not me.

addendum:
the student came back to turn in his paper and continued to yell at me. when my coworkers did not immediately vocally agree with him, he started to get angry at them as well. He said that he'd never had trouble with our office before, but now he saw why everyone complained about hating us. He asked me if I was having a bad day, had any emotions, and/or was a robot, among other rude comments. He actually confronted my two coworkers, demanding to know if they were used to this behavior all the time, and didn't they have a problem with it. when my coworker Lori said gently that it seemed he was overreacting and asked if he had not slept much in the past few days. He really went ballistic then. He finally left. it's a little freaky. there's been enough school shootings and such by now that a little caution doesn't hurt. I wish I could feel that I deserved it in any way, because then it'd be more understandable and less freaky. oh well. anyone want to buy me a bullet-proof vest for Christmas?