It's Marxist because it explains inequality by claiming (with no direct evidence) that society is split into two sides, and there's a conspiracy by one group to

It's Marxist because it explains inequality by claiming (with no direct evidence) that society is split into two sides, and there's a conspiracy by one group to oppress the other which justifies the use of unfair tactics to take the wealth of the oppressors and give it to the oppressed. If some members of that latter group stand up and say they aren't actually being systematically oppressed, it is explained as treachery or that they are unaware of their own oppression. IOW if you replace class with race/gender then it's the same world view, teachings and moral code.