I feel like I need more context here. Humanism is defined by Wikipedia as a philosophy emphasising both human well-being and potential. That doesn’t provide an immediate connection to the tolerance paradox.

There is only a tolerance paradox if you treat tolerance as a moral absolute. That is, if you treat tolerance as something you must give to everyone regardless of their actions (or anything else), then you run into the paradox that giving tolerance to those who do not reciprocate it actually undermines the nature of your own tolerance by forcing you to defend the intolerant.

However, if you treat tolerance as a social contract, there is no paradox. Everyone deserves tolerance so long as they are willing to give it in return. If someone is unwilling to be tolerant, then they do not deserve tolerance themselves. No paradox.

No.

Tolerance is not paradoxical.

It's a social contract and those who break it aren't protected by it.