Thank you for this comment, Horst.

I agree that fundamentalism is about power. Fundamentalist Christians, just like fundamentalist Muslims, Jews, or Hindus, are authoritarian groups trying to seize power by promising to purify their church. Politics and religion is always a bad mix.

Where belief fits in, that's a psychological question. To tell someone they can't be part of your group unless they believe X, Y, and Z is a manipulative mind game, and a dangerous one.