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. […] We should therefore claim, in the name of tolerance, the right not to tolerate the intolerant.
Karl Popper, The Open Society and Its Enemies (1945), Vol. 1, Notes to the Chapters: Ch. 7, Note 4.