The foothold of Marxism in the US seems to be among upper-middle class liberal intellectuals, again like myself, who would seem far too attached to the system they claim to abhor to constitute a national security threat.
Although I just recently learned the ideological distinction between the Bolsheviks and the Mensheviks, that the former believed in a professional revolutionary class (vanguard/cadre, Leninism) while the latter believed the revolution should be more natural and the collective should be left to somehow speak for itself.
Before learning this I was under the impression that the schism in 1903 was due to some semantic argument about what constitutes the duties of a party member.
So having an upper-middle class stratum of revolutionary theorists would seem to be in keeping with the Bolshevik approach, which I suppose makes sense seeing as they ended up being more powerful than the Mensheviks, and by extension a greater determinant of the legacy of Marxism, to my knowledge.
Maybe if it went the other way, Marxism would be a less theoretical and bourgeois project, i.e. more of a threat to the status quo of wealth inequity and the private ownership of means of production.