No content but the video. But "why do stupid people think they are intelligent"? Because they think they are intelligent.

In one office, I had the misfortune to be "acting" when a routine report about average office space per employee crossed my desk. Being a curious type, I checked the math. It was wrong. I called the analyst in to ask about it. It turned out that she didn't really understand how to use a computer spreadsheet. She just treated it as a form to fill out. She did all her work of a calculator and typed the numbers in.

She was averaging unequal numbers. Let's just say one Region had 100 employees and another had 1,000. She treated their average sq ft the same. Because she didn't understand how to use the computer to sum columns. The averages were way false and had been all the years she "managed" the program.

I tried to explain how to check her numbers and use the computer functions. She considered that we were "debating" the right way to measure them. I had to explain that I was "correcting" her errors, not debating how they should be done. When the Boss got back, all Hell broke loose. The correct numbers were bad for the office. But everyone agreed that I was right, without any doubt.

And she kept her job, doing things wrong. And she still thought she was right because her method was "easier".

That's what DAMNED STUPID is.