Many are familiar with Karl Popper's "The Paradox of Tolerance." If you're not: briefly, if we are tolerant of intolerance, intolerance will grow and kill tolerance.
But it's not really a paradox, it's simple logic: intolerance of intolerance *is* tolerance (a negative of a negative is a positive). The problem is many (not all) intolerant types don't understand they are intolerant. Their indecency and ignorance just "makes sense" so they are incensed when tolerant folk go after them.
3/x