Marx, Enemy of the Constitution?

Is it constitutionally permissible to hold a Marx reading group in the German Republic? According to a recent judgment of Hamburg’s Administrative Court: unclear. A reading group can apparently only take place as long as it does not “actively and combatively” promote Marx’s ideas, since “the social theory formulated by Marx” is in essential points “incompatible with the principles of the liberal democratic basic order” of the Federal Republic. The judgement is worth examining in detail.