Maybe you don't read much, but it's obvious they weren't making some universal statement about code. They are referring to the code you write when you are just experimenting by yourself, for yourself. The point is to not let irrelevant things like usefulness, quality, conventions, etc. limit just tinkering and learning.

Stupid code is fine. Make it work/exist first, you can make it good later.

Yeah, I think he’s trying to equate it to something like “there are no stupid questions.” That’s a pretty silly analogy, but you get the idea.

when you're paralyzed into not putting anything on the page, it's important to just get the dumb idea onto the IDE and refactor from there.

I think the people who think there is no stupid code don't actually ever witness truly bad code. The worst code that they come across is, at worst, below average. And since that's the worst they see, it gets mentally defined as bad.

He will counter with "There are no stupid sentences"!