So goes the argument. I don't think the author has really proven it, it was pretty theoretical. It's not clear the tiny minority won't just weaponize the powers that be to silence those that disagree with them even further.

That said, I don't think free speech is a utilitarian principle (greatest good for the greatest number) but rather a deontological one, that it is wrong to muzzle an individuals right to express themselves as a first order effect. The author's argument describes second or nth order effects.