I like Zizek’s take on tolerance
Why are today so many problems perceived as problems of intolerance, not as problems of inequality, exploitation, injustice? Why is the proposed remedy tolerance, not emancipation, political struggle, even armed struggle? The immediate answer is the liberal multiculturalist's basic ideological operation: the "culturalization of politics" - political differences, differences conditioned by political inequality, economic exploitation, etc., are naturalized/neutralized into "cultural" differences, different "ways of life," which are something given, something that cannot be overcome, but merely "tolerated."
I saw it explained this way: with square tiles, for example, you could shift the pattern over a certain distance (say one square width to the right) and the tiles would line up perfectly with the original. With this tile, you can’t ever do that.