The shorter version is: Eeek! Marxism!!
Silver sets up a binary between "rational progressivism" and "radical progressivism." Even if I hadn't learned from Derrida to treat all binaries like Trojan horses at best and blatantly hegemonic thought-oppressors at worst (thanks, Jacques!), the terms Silver selected give away which end of this binary he's going to endorse. If you can't guess, let's take a look at the table he creates to distinguish these types:
Silver goes on to describe each type in more detail, consistently undercutting the radical side of the equation, ending up with this:
The truth is, I don’t particularly care whether you call me a “progressive” or not. In fact, I'm suspicious of people who line up on the same side of the ideological divide on every single issue. The world is more complicated than that, especially when one strives to see the world through a scientific, empirical lens. While progressives, in my view, clearly have the preponderance of good ideas, they do not have a monopoly on them. Nor do conservatives have a monopoly on bad ideas, especially when radical progressives flirt with Marxist modes of discourse.Silver's attempt to oppose "Marxist modes of discourse" with "scientific, empirical" analysis lays bare a tremendous indifference to a lot of actually existing Marxism, substituting for it a bogeyman borrowed from the conservative imagination. I would submit that maybe DailyKos and OpenLeft are not the interlocutors Silver should be engaging with, and that taking them as the intellectual standard-bearers of Marxism or the Left is kind of silly when he could be taking a look at someone like David Harvey and working through The Limits of Capital.
Attempting to split the Left with a characterization cribbed from the Right is not going to help "rational progressives" win anything—elections, reform, even ideological debates with conservatives. Well, it might "win" some blog arguments, but the idea of "winning" an argument on a blog is like winning a kissing contest at a family reunion—doesn't everyone just end up feeling icky? And what's the prize, really?