"Cindy Sheehan, the mother of Casey Sheehan, an American soldier who was killed in Iraq.."

That's the sentence Cindy Sheehan and her increasingly lugubrious PR machine want every news story about her to begin with. Nobody likes the idea of criticizing a woman who's lost her son in such circumstances. The hope has been that the high wall of Mrs. Sheehan's "moral authority" will allow her to say whatever she pleases and that nobody will say boo about it for fear of seeming insensitive to what must be unimaginable anguish. Still, even some of her supporters must realize that her anguish has caused her to find meaning in a wildly partisan, orchestrated publicity stunt.

What's interesting, to me at least, is that Mrs. Sheehan represents simply the latest installment in a long, nasty, desperate ideological campaign - and one that demonstrates the logical limits of identity politics.

Anybody who's been on the receiving end of the "chickenhawk" epithet knows what I'm getting at. Various definitions of chickenhawk are out there, but the gist - as if you didn't know - is "coward" or "unpatriotic hypocrite." The accusation is less an argument than an insult.

It's also a form of bullying. The intent is to say, "You have no right to support the war since you haven't served or signed up." It's a way to get supporters of the war in Iraq, the war on terror, or the president simply to shut up.

But, there's a benefit of a doubt to be given. There are many people - I know because I've argued with lots of them - who don't believe the "chickenhawk" thing is intellectually unserious.

Obsessed with "authenticity" and the evil of hypocrisy - as they see it - they think the message and the messenger are inextricably linked. Two-plus-two is four only if the right person says so. We hear this logic most often from adherents of identity politics, who give more weight to the statements of women, blacks, Jews, and others for the sole reason that they were uttered by people born female, black, Jewish or whatever. People who grew up poor are supposed to have a more "authentic" perspective on economic policy than people who didn't, and so on.

Don't get me wrong - experience is important and useful, including the experiences that come from being black or gay or otherwise a member of the Coalition of the Oppressed. But valuable experience confers knowledge, it doesn't beatify. And identity isn't an iron cage. It is not insurmountable. And, at the end of the day, arguments must stand on their own merits, regardless of who delivers them. Continued...