The problem with the idea that sometimes people are better of not knowing is that it has no practical impact on how an ideal rationalist should behave, even assuming it’s true. By the time you’ve learned something you’d be better off not knowing, it’s too late to unlearn it. Humans can’t really do doublethink, and especially not at the precision that would be required to be extremely rational while using it.
The problem with the idea that sometimes people are better of not knowing is that it has no practical impact on how an ideal rationalist should behave, even assuming it’s true. By the time you’ve learned something you’d be better off not knowing, it’s too late to unlearn it. Humans can’t really do doublethink, and especially not at the precision that would be required to be extremely rational while using it.