Belief-Systems - A Mixture of Divine And Human Content

Let's pretend for a moment, we humans were capable of space-travel and reached another planet. There we found human like beings, who, just like us, follow spiritual teachings.
There is one group, that believes in a system that is based on categorizing people into groups. The members of the highest are seen as almost god like, those of the lowest are less valued than some animals.
There is another group, whose teaching is so esoteric, that only very few people within that group really understand it. To most people outside of that group, their teachings are to removed from real life. And many ordinary members just follow some rituals, never understanding the real content.
The next group thinks, that anybody that doesn't join their group is to be killed. They make their men wear something that looks like a cardboard box, that sits on top of their head, and reaches all the way to the ankles. They say, their women would be to tempted to engage in mating rituals with any man coming their way, if they saw the actual shape of him or his face. So the women hide the men at home, don't want them to contribute to the family income, and treat them like property or slaves.
And another group follows the teachings of a person, who's core message originally was “love”. However, that same group has raged the bloodiest wars in the history of that planet. There are several sections within that group, and each section claims to be the “true” followers, whereas the other sections are just fakes. The members of this group publicly display their worship symbols, but get very offended, sometimes even aggressive, when they see a symbol of another group displayed.
And yet another group is very exclusive. Only the children of the members are accepted as real members. The rest of the population of that planet is seen as kind of a “filler”, just to reach the numbers to make the economy work.
Think about that. Independent of any other potential content that the teachings of any of these groups might include, can you imagine, that the people of that planet could ever reach a state, where they would be able to live together in peace and harmony?
I can't believe, that a truly divine spirituality would include any of these ideas. There must have been something gone wrong! Maybe the founders of the various groups didn't know the whole story themselves. Maybe they added some of their cultural background into their message. Maybe followers didn't understand some of the ideas, or misinterpreted some of the messages. Or maybe, over time some non-divinely inspired content got added.
If you were to be asked, what you would recommend the people on that planet should do in order to make progress on their spiritual wisdom? How could they cleanse their belief-system of non-divine content?