Alas, it's the same long-discredited nonsense as usual. Massimo doesn't know what he is talking about. I think at this stage one has to regard Massimo's writings as a case study in cognitive dissonance. How will Massimo continue to reconcile his doubts about Darwinian cultural evolution with the views of all the scientists who are now taking it seriously?
Massimo cites Lewontin's 1970 article "The Units of Selection. Explaining why he doesn't think the principles it lays down apply to cultural evolution. However, what he neglects to mention is that Lewontin stated himself that the principles did apply to cultural evolution in that very article. Here's what Lewontin said in 1970, on page 1:
It is important to note a certain generality in the principles. No particular mechanism of inheritance is specified, but only a correlation in fitness between parent and offspring. The population would evolve whether the correlation between parent and offspring arose from Mendelian, cytoplasmic, or cultural inheritance.
If you cite an article to support your position, and the author of the article disagrees with you in the same article, you should at least point that out.
Massimo's headache reminds me that one thing we haven't seen very much of so far is people publicly changing their mind on the topic. We clearly have a new generation of researchers who grew up with memes and understand the topic - but I've seen very few previous critics turn around and confess that they were mistaken. If scientists die before they change their minds on this topic, then we might be in for quite a lot more Darwinian revolution.
Update 2015-12-03: Massimo gloats over the reception of his paper here. It is all very well bending over backwards trying to find sympathetic interpretations of your opponents perspectives - but it is best not to bend over too far.