@andrew I think it's important to distinguish between "tolerance of ideas that I disagree with" and "tolerance of ideas that are themselves opposed to tolerance".
The first case helps nurture a venue for vigorous inquiry into the truth.
The second case allows the venue itself to be demolished.
It's the difference between allowing access to the well and allowing the well to be poisoned.
As has been pointed out elsewhere, tolerance is a contract -- an extension of trust. When someone uses that trust to advance intolerant ideas, they have broken the contract and are no longer party to its benefits.
andrew