If you have a problem with this question you have a problem with John Stuart Mill's On Liberty, which has stood the test of time for a reason, and I propose such people look up Heterodox Academy https://heterodoxacademy.org, started by Jonathan Haidt among others.

They released the relevant parts of On Liberty I recommend https://heterodoxacademy.org/mill.

Without diversity in viewpoint, you don't know what you know or not, and when you face someone with an opposing viewpoint, you find yourself impotent and confused. They will likely beat you in debate and influence others more effectively. Your emotions may become intense, undermining your ability to bring others to see your view. Challenging your own ideas teaches you and strengthens you.