Wiki - The paradox of tolerance states that if a society is tolerant without limit, its ability to be tolerant is eventually ceased or destroyed by the intolerant. Karl Popper described it as the seemingly self-contradictory idea that in order to maintain a tolerant society, the society must retain the right to be intolerant of intolerance.
I sometimes make fun of reactionaries by saying “Anti-Racists are intolerant of Racists. They’re the true racists!”. Didn’t know there was a point to be made in that joke!