[Garoof]

"We expect answers to be supported by facts, references, or specific expertise, but this question will likely solicit debate, arguments, polling, or extended discussion."

He's asking for free books about programming. When someone answers with a book, it's super-easy to verify that it is a book, is about programming, and is free.

It might be a bad fit for SO because there isn't one answer that is "more correct" than all other answers and so on, or something like that. But it is not a question that leads to arguing and extended discussion. It's a question that leads to people posting links to free books about programming.

So like, it might not be arbitrary and it might be that all the right questions are being closed, but it looks like a bunch of deletionists flailing about, knocking shit over. And it looks like that because there's this canned "reason" for closing a question, and it is often a poor match for the question being closed. Not because people don't get that SO is "not meant for discussions".

[insteadof]

It at least definitely leads to polling. Everyone and their capuchin being able to just throw in theirs as a legit answer. When there is no chance for a canonical answer at all, that's a bad question.