If everyone is tolerant of every idea, then intolerant ideas will emerge. Tolerant people will tolerate this intolerance, and the intolerant people will not tolerate the tolerant people. Eventually, the intolerant people will take over and create a society of intolerance. Therefore, Popper said, to maintain a society of tolerance, the tolerant must be intolerant of intolerance… hence the paradox
Karl Popper, Mark Manson