Why do religious nuts make such good antagonists in horror films?

I think it is that in times of pressure,extreme circumstances or supernatural scenarios, that those with strong religious beliefs tend to be aggresive more than assertive with sharing their beliefs. The weaker minds around them mistake it for true leadership in their fear and confusion. The fact that the zealot can gather people behind them makes them dangerous because the people will start to follow anything else said to them in the name of survival/salvation. Even to the end that people that wouldn't nornally listen to such a person or chose such action on their own, will turn away from their own logic in a state of panic, and more often than not cause their own downfall in surrendering their independance and free-will.

A great example is the movie "The Mist", when Ms. Carmody starts preaching woes and repentance, and even leading to sacrifice.

You will also notice a tendency for people to follow such extremists like a moth to a light, yet see how quickly their allegiance scatters when that "light" is removed.

Because religious nuts are terrifying. You never know how far they'll go or what they'll do. Just look at the Westboro Baptist Church. Also, they're pretty annoying most of the time.