So here is a definition to start off with:
The capacity for or the practice of recognizing and respecting the beliefs or practices of others.
The problem is that people misunderstand tolerance. Oh, don't get me wrong, it's a good thing. But tolerance is something that you offer, grant, provide. And you expect it in return. It is absurd in the extreme to refuse to offer it and to nevertheless expect it offered to you by those you've metaphorically exiled.
Having hated non-whites, supported segregation, opposed Martin Luther King Jr, and actively supported apartheid, one might have expected that the late Rev. Falwell would have learned some humility in the process of backing away from that shameful personal history. But no. Gays, liberals, followers of other faiths, and many others were folks he publicly reviled and declared collectively responsible for catastrophes like 9/11.
That's preaching intolerance.
Tolerance is a form of social contract. We agree to cut each other slack--a lot of slack--and to accept, acknowledge, put up with and ignore... as good neighbors do... the differences among us. We don't insist that they be just like us, do just like us, and think just like us. It's ok, you're different from me, and we're different from yet a third person. But insofar as we can live with each other and do each other no harm, insofar as we can civilly negotiate the inevitable conflicts among ourselves (and this is no different than living in a family where everyone's quirks and foibles have to be dealt with), we can allow each other a great deal of latitude.
Jefferson famously observed:
But it does me no injury for my neighbor to say there are twenty gods or no God. It neither picks my pocket nor breaks my leg.It may be something I disagree with, but it does me no harm. So I can, should--and must, in a society that is tolerant--tolerate a view I think wrong... at least if I want to have any claim on being tolerated myself. Tolerance is a form of reciprocity.
This is where the claim on tolerance by, and on behalf of, the intolerant absolutely founders. You are entitled to tolerance by signing onto the implicit deal. We tolerate each other. But those who refuse to be tolerant have no claim on the tolerance of others. It may be extended, but if it is, it is a gift--and there is no right to a gift.
Falwell and his apologists have no claim to our sympathy and tolerance because they are not "in the game" as participants. Instead, they are predators or parasites on a system which functions well because of its broad tolerance. They want the benefits, but don't want to give back.
And for that, there is no tolerance.