An incident at work today

Keeping in mind that I hate Sunday's because we sell a ton of newspapers (people who buy newspapers are assholes. They don't have to speak to you, and if there is a line I guess they have the right to cut in front of everybody, power bomb their money onto the counter, and run out before you can say anything to them). We will just call the customer I am speaking of Large Richard, because he was a dickhead. With that said the following incident ensues:

Me: Hello
Large Richard: Hi (walks over to newspapers) You don't have the Detroit News?
Me: Sir, the Detroit News does not put out a Sunday paper
Large Richard: Since when?!?!?!
Me: Probably about 3 or 4 years.
Large Richard: (approaches counter and pays, then begins to walk out but realizes he wants a Macomb Daily too) I will get a Macomb Daily too.
Me: Okay. $1.50 please
Large Richard: It's $1.50? $.50 more than the Free Press?
Me: Yes
Large Richard: That's fucking bullshit. (hands me a $5.00 bill)
Me: Okay sir.
Large Richard: Oh, I found $1.50. Is that okay or will it screw you up?

It is at this point that I am getting pissed. You can come in and act like a douchebag, but when you question my mathematical skills, it is fucking on. You see the rage? This man has me swearing in the context that is not a direct quote. Anyway, the transaction continues.

Me: No sir, luckily in my college coursework I have acquired basic math skills.
Large Richard: (scoffs) A lot of good that has done you. You work at 7-Eleven. (Proceeds to laugh at me and walks out)

When people talk to anybody, not just me, in this manner, I would love nothing more than to knock their teeth down their throats. What gives anybody the right to go around treating others like dirt? Take a look at yourself. People who frequent convenient stores are lowlife scum, and they have the audacity to pass a judgment on anybody? My advice: Go drive your car into a tree you piece of shit.