Religious and spiritual labels are just another shortcut way for humans to justify negative or simplifying thoughts or actions towards another. People come down on one another for representing a common label 'poorly', or for not having the 'right' label at all. Labels try to define a big picture, but even amongst people of the same religion/beliefs the big picture is not the same, unless they spoon feed on what they're told without contemplation. To know what being ______ means to one person, you have to dig and find out what their smaller more discrete beliefs/moralities are, in relation to what _____ is 'supposed' to make you believe.
After a point, belief is not worth arguing over. It can only be held in the face of doubt, not in the blinding glare of truth. I find it much more interesting to contemplate the similarities between belief systems than to become mired in their differences
Assholes make things shitty for any group, including religious/spiritual/belief groups. Assholes also have a propensity for getting into groups, to use the association to raise their assholery to new heights. Assholery crosses all lines, and is the true problem that humanity has faced since the dawn of civilization.
Stalin, was one of the biggest assholes ever to live. Don't forget the ~7 million Ukrainians he genocided by starvation. He was an egomaniac who had people taken out of pictures as he had them 'removed' from society or life. Stalin was a Stalinist, his regime was a cult of personality veiled behind Socialism.
Marx didn't have the worst ideas about how people should get along. Noone can really mask how easily people corrupt something good, given power. Also, if you read about Marx's life, you'll figure out he was kind of a scrub.
The only people-labeling system I've ever needed is: "asshole" or "duder".