Here is a deft essay by Stephen T Asma on the role played by monsters (and Zombies!) in helping us deal with real-life extreme people and situations:

You can't know for sure how you will face a headless zombie, an alien face-hugger, an approaching sea monster, or a chainsaw-wielding psycho. Fortunately, you're unlikely to be put to the test.

But you might face similarly terrifying trials. You might be assaulted, be put on the front lines of some war, or be robbed, raped, or otherwise harassed and assailed... And though we can't know for sure how we'll face an enemy soldier or a rapist, it doesn't stop us from imaginatively formulating responses. We use the imagination in order to establish our own agency in chaotic and uncontrollable situations.

And this:

In 2006, four armed men in Kandahar, Afghanistan, broke into the home of an Afghan headmaster and teacher named Malim Abdul Habib. The four men held Habib as they gathered his wife and children together, forcing them to watch as they stabbed Habib eight times and then decapitated him. Habib was the headmaster at Shaikh Mathi Baba high school, where he educated girls along with boys. 

... My point is simply this: If you can gather a man's family together at gunpoint and force them to watch as you cut off his head, then you are a monster. You don't just seem like one; you are one.

A relativist might counter by pointing out that American soldiers at Abu Ghraib tortured some innocent people, too. That, I agree, is true and astoundingly shameful, but it doesn't prove there are no real monsters. It only widens the category and recognizes monsters on both sides of an issue. Two sides calling each other monsters doesn't prove that monsters don't exist.

Quite. Read the whole thing.