The core point is, if you have a society that accepts anything and everything, that society will not end up with all the things, because it'll also accept people working explicitly to get rid of some of the things. It will instead end up with few things, being run by "dictatorship of small, intolerant minorities"[0]. Therefore, if the society wants to stay accepting, it has to carve an exception - it needs to reject anyone who doesn't also accept anything and everything.
Reasoning behind the "paradox" is sound, but its application to real world varies. In particular, I've recently noticed that the "paradox of tolerance" is primarily being wielded by small, intolerant groups that want to aggressively force their way on everyone else.
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