Elitist language can be used by any group to partition themselves from others. I'm sure many groups (formal and informal) do it.
That said, I believe there has to be a floor to the language level you choose, and it's reasonable to use "high school English" as that floor. Besides, I checked out that link (history section) and didn't see anything that screamed "overly clever"...
The comparison to marxist texts is more pointed if they were unapproachable not just to the layman, but to people proficient in (non-marxist) political economics -- which is arguably the case.
I'm not sure why that's ironic. Extremists tend to have a lot in common in their overall approaches, even if they may be violently opposed on the specifics.
That said, I believe there has to be a floor to the language level you choose, and it's reasonable to use "high school English" as that floor. Besides, I checked out that link (history section) and didn't see anything that screamed "overly clever"...