Leftists have a bizarre tendency to view early 20th century German history in an almost religious context. They ignore the specific historical, economic, and social conditions that caused the rise of Nazism in 1930s Germany entirely. They instead see Nazism as proof of the existence of a kind of metaphysical demonic force they have to perpetually and vigilantly perform cultural exorcism against to prevent it from coming back.
This is then given teeth with the concept of the "paradox of tolerance" - of course, what the paradox of tolerance actually demonstrates is that unlimited tolerance is a self-defeating concept. Instead of taking away from this "making tolerance your highest moral principle is unviable", they instead come to the oxymoronic conclusion that"we have to be intolerant of intolerance".
Of course, another way of phrasing this is "we have a justification to suppress values we don't agree with" - the end result of that isn't preserving a tolerant society. Instead it allows them to label the beliefs of their opponents ("we shouldn't troon out kids", "we shouldn't flood our country with millions of people from incompatible cultures", "we shouldn't allow junkies to shoot up in public parks", etc.) as "intolerant", giving themselves a license to suppress them.
