How to deal with angry people

A man stormed into my office this morning, red-faced and thick-fisted. He looked like he was in his fifties, and he had a barrel chest and huge muscular arms. I took notice.

"You stole my idea!" he barked, pointing a thick accusing finger at my face, sweating heavy, itching for a fight.
"what idea?"

"Fiction! Talking about things that did not happen, but describing them anyway! You stole it!"

I raised by eyebrows sarcastically. "People have been doing that a long time."

He didn't slow down, "well, I was definitely doing it before you, and I thought of it myself!"

It was just one of those times, you know? I held out calming hands, "Okay, I'm sorry. Tell you what. I'll placate you by telling you my deep insight into the world."

I think he was just looking for an empty apology, because he calmed down immediately. "Fine."

"Okay," I said calmly, "Here's my insight. There's two types of people in the world. People who steal rubies from little kids and use the money to start a business selling salad online, and people who roll around in big swimming pools full of salt while loudly debating the merits of Charles Darwin's theories."

He growled. "What about all the people who don't do either of those things?"

"Drat," I said, "I knew I was forgetting something."

Man, I'm in big trouble now! Any advice?