No, try reading it again. "So if you decide someone is stupid, it means you’re not thinking, which is not being smart."

"Not being smart" != "is stupid" is exactly the distinction he is making.

I'm well aware of the words he chose. I am referring to his actual meaning.

The fact is that there are stupid people on this planet. The fact is that we can know there are stupid people. The fact is that we can identify a stupid person. And it is utterly stupid to pretend otherwise. He's made a very stupid generalization based on the behavior of the masses -- yes, most people who call others stupid are themselves stupid. But that doesn't mean we can't know who is stupid nor does it mean that it's wrong to call someone stupid.