The "Paradox of Tolerance" completely disappears if you look at tolerance not like a moral standard but as a social contract.

If someone does not abide by the terms of a contract, then they aren't covered by it.

In other words, the intolerant are not abiding by 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.