> But we should claim the right to suppress them [intolerant ideologies] if necessary even by force; for it may easily turn out that they are not prepared to meet us on the level of rational argument, but begin by denouncing all argument; they may forbid their followers to listen to rational argument, because it is deceptive, and teach them to answer arguments by the use of their fists or pistols."
https://en.wikipedia.org/wiki/Paradox_of_tolerance
It came from Karl Popper, the guy better known for philosophy of science and using "falsifiability" as a primary criteria for what's science/not-science.
That the "free speech" crowd that said "we must allow all hateful and intolerant speech" sure does seem to quiet up when those advocating for open societies get silenced!