They are not culturally productive in their hidden fastnesses. Their games, culture, artifacts, and practices are cribbed from the larger muggle culture - suitably modified, of course, to reflect their peculiar abilities. In short, culturally speaking, they are parasites. One suspects that they are economic parasites as well, leaching off the muggle world. One would expect them to be - they have the slaveholding mentality - but there is not enough evidence in the extant narratives from which to make a judgement.
I thought that Marxists (the male ones, anyway) get laid more than other lefties because they have this macho bolshy air of masculinity about them, unlike, say, weedy vegetarian dreadhead types. With the possible exception of the Guevaraites, who get extra rock-star points.
(References: <I>He Died With A Felafel In His Hand</I>)
Dunno about the blokes, but I'm not a big fan of the chicks (ooo oppressive language tut tut) from Resistance.
I'm no fan of any dogmatists myself. IMHO, Marxists are the same sort of deal as Christian Fundamentalists or Objectivists or what have you.
Speaking of fringe-lefty hair-splitting, I'm reading Ken MacLeod's _The Stone Canal_ right now. Highly recommended.
Marxists never get laid. Hence they spend their copious amount of spare time writing bullshit critiques of childrens books. So what it it fails to subvert the dominant paradigm! It gets kids to read instead of watching TV, so leave it the hell alone.