From Andrew Sullivan's new Salon piece on Harry Belafonte:

the essence of bigotry is to reduce the complex, varied, human individuality of a human being into a racial cipher. It is to smelt the irreducible complexity of a person into a racial caricature. It is to deny individuality; it is to give someone no space to think for him or herself, to free to be a person, and not a mere member of the group.

To me, this freedom is an irreducible core of what liberalism should be. It is about a person's right to think for herself with dignity and respect. It doesn't mean that you can't disagree vehemently with such a person, subject her views to withering scrutiny, rhetorical barbs or logical dissection. What it does mean is that you do not play the race card or any other card when engaging that person's views. And one of the key signs that much of today's left is actually, demonstrably illiberal, intolerant and reactionary, is the way in which this is now a common feature of leftist discourse.

There's much more.