If a leader makes it clear (even implicitly) they only want confirmation bias, that's exactly what they'll get.

They'll think they're getting real information, but it's total slop.

The more that no one else tells them disconfirming evidence, the more that the incremental person will see it's dangerous to tell them, too, and will be even less likely to share.

A ratcheting supercritical state until reality crashes in, and that crash might kill you.