Leftists worry about Beinart because of his friendship with Jonah Goldberg but they have no need. Beinart is just your typical over-educated Trotskyite who will never renounce Marx but cannot quite figure out why the Left is such a massive failure in everything they do.
Like his boss Peretz he is a mass of unresolved internal conflicts and ambivalence. He drinks the champagne that free markets make possible but will never forgive them their success.
Umm, actually he specifically blasted those who think that the left should be close to Communism, and said that in his view the left needed to be the furthest thing from both communism and fascism. (I personally think that's kinda a silly scale, fascism and communism are virtually identical in practise, and only different even theoretically in the retoric they use, but that's not the point)
I don't agree with him on most things, but if the rest of the left thought like Beinart, I at least wouldn't be in 24hr panic mode. He at least recognize that America is not the enemy, and that we shouldn't be fighting over what America is, just what it should do.