Why would screening off entire categories of ideas lead to a systematically incorrect view of the world? Or why would entertaining those ideas lead to a less incorrect view of the world?
It stops you from noticing what other people believe and why, which stops you from understanding them even if you ultimately believe they're wrong.
Which pressures them into either keeping it to themselves or being pressured by society to change their beliefs. The “respect everyone’s opinion” is how we got Charlottesville. Tolerance can and should have limits.