Ramesh, that is a very interesting — albeit too brief — piece. One objection I would raise is how Barnett ends it. He writes:

Many in the conservative blogosphere have been quick to label Kos a “moon bat” because of his unforgiving left-wing politics and his strident tone. Kos in turn dismisses these critics as “wing nuts.” (Who says dialogue in the blogosphere isn’t edifying?) This kind of juvenile give and take, however, obscures the vital fact that Moulitsas leads an influential movement, a movement whose influence is likely to grow even larger.
Whether or not that’s good for the Democratic party remains to be seen.

It seems to me that whether it’s “good” or “bad” for the Democratic party is at best a secondary issue. The first question is whether it’s good for America and it seems to me that it’s objectively bad, at least from the perspective of the Standard or NR. As you’ve written, it’s not necessarily good for conservatives when the Democrats move to the left, even it is good for Republicans. What Barnett is identifying is a very troubling trend among Democrats to prositute their (alleged) principles to the neo-McGovernite/Michael Moore populist left. And that’s not good. Period.