Nitpicking, but the quote stated that people who are on neither offensive nor defensive are people you can learn from - it didn't say that people who are on the offensive or defensive are necessarily wrong to do so.
I'm not sure that's just a nitpick. It's a mistake so common that it should probably be listed under biases. It might be a variation on availability bias-- what's actually mentioned fills in the mental space so that the cases which aren't mentioned get ignored.
Another month has passed and here is a new rationality quotes thread. The usual rules are: