Roman Catholics, Orthodox and fundamentalists fear Donald Trump's Protestantism

Here, here, and here, just to name three recent examples: Trump can't be a good Christian according to Cardinal Dolan because he supposedly doesn't welcome the stranger, or doesn't have a high enough view of the Lord's Supper, or hasn't repented and been born again.

Mitt Romney's Mormonism was supposed to be off limits in 2012, but suddenly fellow Christians get to pile on Trump.

Better watch out. He's been known to fight back.