A lesson in courtesy

Courtesy of my friend Tex, this:

An old prospector shuffled into the town of El Indio leading a tired old mule. The old man headed straight for the only saloon in town to clear his parched throat. He walked up to the saloon and tied his old mule to the hitchin' rail. As he stood there, brushing some of the dust from his face and clothes, a young gunslinger stepped out of the saloon with a gun in one hand and a bottle of whiskey in the other. The young gunslinger looked at the old man and laughed, saying, "Hey, old man, you ever danced?"
The old man looked up at the gunslinger and said, "No, I never did dance... Never really wanted to."
A crowd had gathered as the gunslinger grinned and said, "Well, ya old fool, you're gonna' dance now," and started shooting at the old man's feet.
The old prospector, not wanting to get a toe blown off, started hopping around like a flea on a hot skillet. Everybody was laughing, fit to be tied.
When his last bullet was fired the young gunslinger, still laughing, holstered his gun and turned to go back into the saloon. The old man stepped to his pack mule, pulled down a double-barrelled shotgun, and cocked both hammers; the two loud clicks carried clearly through the desert air.
The crowd stopped laughing immediately. The young gunslinger heard the sounds too, and he turned around very slowly. The silence was almost deafening. The crowd watched as the young gunman stared at the old timer and the large gaping holes of those twin barrels.
The barrels of the shotgun never wavered in the old man's hands as he quietly said, "Son, have you ever kissed a mule's ass?"
The gunslinger swallowed hard and said, "No, sir, but I've always wanted to."

There are two lessons here:
Don't waste ammunition.
Don't fuck with old people.