The paradox of tolerance disappears if you look at tolerance not as a moral or legal standard, but as a social contract:

If someone does not abide by the terms of the contract, then they are not covered by it.

In other words: the intolerant are not following the rules of the social contract of mutual tolerance.

Since they have broken the terms of the contract, they are no longer covered by the contract, and their intolerance should NOT be tolerated.