It's a lot like a religion. Purity tests, dogma, things you can't say, good vs evil, self-flagellation, original sin, kicking people out who don't conform...
Definitely a lot like religion. I really recommend the book "Christianity: the first three thousand years". Post historical crucifixion of Jesus the first few hundred years of Christianity sound like a purity spiral, monarchism, gnosticism, origenism.
The original church in Antioch first applied the word catholic to Christianity (καθολικός / katholikos) but was then later ejected from the western church in 1054 for not being catholic enough.
