I suspect that the problem actually stems from Liberal morality. Liberals operate primarily in two points of the six points of morality; that being liberty and compassion. They are not opposed to things like loyalty, authority, sanctity, or karma--but they will toss those aside without a second thought for the sake of compassion. Even liberty will be thrown aside for compassion.
And that explains communism. The ideology is based in the concept that people will be good (compassionate) to each other, while supplying the maximum amount of liberty possible. The most common trap of attempting to achieve this (besides the fact that it's impossible) is that very often someone of dubious morality takes over. The second, less common trap--which is more of a long-term, slow boil as you see in the West (or China), rather than Russia or most Second World nations that attempted this system, is that it actually destroys social cohesion.
Inclusivity is actually not a problem. Diversity is the problem. No one really gets angry that you push to have a black guy at the table. And the black guy will be welcomed if you make him seem and act a lot like the other people at the table. The differences do not seem so big. If on the other hand, you not only have the black guy sit down, but then lecture how the black guy was oppressed by the rest of the table for not letting him play, then insist he gets special advantages for having lost out on previous turns, and then you add in two Hispanics and tell everyone that you better not make any jokes or references to Mexico because that's offensive--oh yeah, then a gay guy and transvestite are playing and you have to use these preferred pronouns...
What you've done is not create a unified table of players, but created jaded tribes forced to occupy the same space. People stop mingling and turtle. Or worse, they start joining teams and start attacking each other. And the liberal forcing this whole thing thinks that just because the new people they put on the table will vote his way so they can stay at the table, that suddenly they're all friends. They aren't. Because they won't agree on much of anything else. Because they all lack things in common.
Liberalism is both its own disease and cure. The entire movement will fragment (because it must) and those fragments will not work well together. Then a competing ideology that is cohesive and assimilative will move in and displace them.
I'm sorry, but comparing Marx to Christianity is a bit of a joke. Christianity is actually much more relevant, because it can be applied in someone's daily life. Marxism...really can't. It's all very high concept and when you force people to adhere to its mythology, it horrifically backfires.
