The customer is always rude. And stupid

Recently a customer came in to get his motorbike taxed. Sadly his reminder was out of date because he was a bit late (6 weeks) cos he was waiting for his MOT. I asked him if he had his log book as we could use that to tax it instead. At this point he got the right arsehole and asked (in a pretty stroppy way) where it said on the reminder form that he needed his log book. I politley informed him that because he was so late, his reminder was out of date and the computer we use wouldn't let us issue a tax disc using it. He repeated his request for me to show him where it said he needed his log book on the reminder form. At this point I realised that I was fighting a losing battle and he'd stopped listening to me. Nethertheless, I carried on trying to help him tax his bike despite the increasing amount of rudeness and attitude that was headed in my direction. I asked him if he'd declared the bike as being off road. Nope. It was sitting on his driveway and if that's not good enough for the DVLA then tough. I then told him that he should have declared his bike off road otherwise the DVLA are going to catch up with him and fine him. "But my bike's been on my driveway, I didn't need to declare it off road as you only need to do that if you're not going to use it for six months or more". Where he plucked that load of bollocks from I have no idea. I told him that this was not the case. At this point he flipped, pulled his documents back and stormed off shouting, "You're always coming up with objections to me taxing my bike."
Boo-hoo twat. If you could pick your toys up on the way out I'd appreciate it. If he thought about that last statement for a second, he'd have realised that he was talking out of his arse. It's not in my interest to turn business away. I get paid for doing tax discs therefore I should be trying to do as many as I can (within the law of course).
Taxing vehicles is probably the cause of the most aggro out of all of the transaction we do. If someone hasn't got the right things with them then it's our fault. Not theirs for not reading the form or picking up the wrong bit of paper or not having enough money or being late. I've managed so far not to lose my temper at anyone when they've pulled this sort of thing. It's only a matter of time though. Twats.