Levi has linked to an old review of DeLanda by Shaviro, and both of them agree that DeLanda's hostility toward Marx and Marxism seems rather odd. And I agree with that, but it opens up a moment to talk about polemics.
I think that polemics can be very important. In particular, I think that thinkers, in order to try and think something new, has to clear the way for those thoughts. They have to manage to create some fresh air for themselves, and that breathing room usually comes from taking on one of the master's, one of the great thinkers that help define an intellectual milieu. For DeLanda, that is obviously Marx. For Levi, it is Derrida. For Deleuze, it was Hegel. I could go on (for me, it's Heidegger). Now, these thinkers are obviously to an extent conceptual personae, that is, they refer less to exactly just these thinkers texts, but to an entire relationship, an entire assemblage that goes by the proper name Marx, Derrida, Hegel, Heidegger, etc. All of us think in a field saturated by proper names, even those that refer the most specifically to actual people still refer to an entire assemblage, to an entire conceptual machinery. Their texts, their lectures, their actual students and virtual students, their enemies and teachers, all of these things go into the making of a thinker. The more famous the thinker, the bigger (more powerful, more vital) the assemblage. Sometimes we have to push hard against one of these assemblages, to think or speak something that exists in tension with a localized part of the assemblage. So, I we talk against Heidegger, Derrida, Hegel, Marx, etc. The polemic is necessary for breathing and thinking. That doesn't always mean the polemic is true, at least true against the texts and ideas of a certain thinker whose proper name also names a certain assemblage. I don't agree with DeLanda about Marx, and I don't agree with Levi about Derrida. But I also have little doubt that if they didn't feel the way they did about these conceptual personae, then their work would be very different. And maybe it should be, those are always fine criticisms (fine as in useful or productive). But there is a reason I don't spend a lot of time trying to convince someone they have misread such and such a thinker, unless I think that misreading has come at a cost of thinking something interesting or useful (ultimately this was what Matt was on about in his disagreement with Levi during the so-called Derrida wars. It wasn't primarily about Derrida, but instead about issues of humanism and anthropocentrism).
In the case of DeLanda and Marx, it makes a lot of sense to me even though I find Marx incredibly useful for my work. First, it is clear that many Marxists are far more interested in centralization than DeLanda feels is healthy and useful (think here of Zizek for just a major current example). And I also can't help but share impatience at many Marxists hatred of markets.
While there is no singular entity called The Market, much less The Free Market, markets exist. And markets are powerful tools for decentralized organization. Many on the left oppose cap and trade because it creates a market, and many on the left opposed health care exchanges because it again functioned as a market. I'm not sure how much Marx is to blame for the anti-markets bias, but for DeLanda (following Braudel), markets are powerful and useful tools, and at their heart are opposed to centralization and totalization.