And marx had some fucked up opinions on jews and homosexuals, along with a lot of others in the "Marxist canon" that doesn't mean we throw out the entire ideology because the founder had ideas of race and gender that most people believed before the last century.
The reality is most people who are Christians, like Marxists, haven't read every single book and letter and believe everything that was written. They take the core concepts and apply them to the modern world.
Even the bigoted Christians aren't really orthodox, they aren't following the part that says you shouldn't do usury, they're just bigots looking for a justification for there bigotry. They just Google the verse in the Bible that says gays are bad, just like the small minority of homophobic Marxists will pull up a marx or stalin quote against it.
Religion is a tool, often used by reactionary forces, but has been effectively used by liberation theologians to challenge capital in Latin America.