A customer called me a mother f***er

So, I work at Walmart in the jewelry department. The setup is I have a register with space in front of it to allow customers to check out and a counter behind it for customers to pick out what they want. When they pick their desired accessories, they have to walk around to the front of the register to pay. Because you don't pay the cashier from behind.

Anyway, this really redneck looking guy comes up and wants to buy these black stud earrings. So I told him to please come around to the front of the register. He nods and starts moving, not to the front, but behind me past the counter and pulls out his wallet.

I look at him and say, "Sir, you're going to have to come around here to pay."

He pulls an aggravated face and stomps around to where I told him to pay. When he gets there, he slams his hands down on the counter and says.

"Now why the hell do I have to pay here?"
I start to explain to him before he interrupts me.

"You know what? Forget about it, you mother fucker."
Then he storms off.

I just frown and put the earrings back.