On the Paradox of Tolerance, from The Open Society and Its Enemies, by Karl Popper:
Less well known is the paradox of tolerance: Unlimited tolerance must lead to the disappearance of tolerance. If we extend unlimited tolerance even to those who are intolerant, if we are not prepared to defend a tolerant society against the onslaught of the intolerant, then the tolerant will be destroyed, and tolerance with them.—In this formulation, I do not imply, for instance, that we should always suppress the utterance of intolerant philosophies; as long as we can counter them by rational argument and keep them in check by public opinion, suppression would certainly be most unwise.…We should therefore claim, in the name of tolerance, the right not to tolerate the intolerant. We should claim that any movement preaching intolerance places itself outside the law. And we should consider incitement to intolerance and persecution as criminal, in the same way as we should consider incitement to murder, or to kidnapping, or to the revival of the slave trade, as criminal.
Having lived in Idaho, I have heard too much about the necessity to protect the “free speech” of Neo-Nazis and other hate groups. Earlier this year I was present at the domestic terrorist attack at the University of Washington during Milo Yiannopoulos' speech. Ana Mari Cauce, the school’s president, needs a lesson in philosophy, and what it means to preserve tolerance, by (paradoxically) not tolerating intolerance.
We can protect free speech by letting Yiannopoulos shout on a street corner, but it is in the interest of preserving a tolerant society to not provide the intolerant an amplified and public platform from which they spew their hate. The First Amendment forbids lawful prohibition of free speech. In fact, it is an exercise of our First Amendment rights to protest such an egregious act as passively endorsing the ideas of Yiannopoulos by hosting him. Furthermore, it is not a violation of the First Amendment, nor the idea of free speech, for the University of Washington to refuse to grant an audience to the likes of Yiannopoulos.
I have struggled to make this point because it is so easy to claim that tolerance requires tolerating even hate speech, but Karl Popper makes the matter clear.