Evil is a dirty word.

When you call something evil, you are making a conscious decision not to engage with it. There is no point negotiating with evil; there's no point in talking with it or attempting to uncover some motive behind it. In the absence of good, there is no hope of common ground, no chance of understanding. Evil is beyond our powers of comprehension, so why even try?

When you call a person evil, you absolve yourself of your past and future obligation to relate to that person. When you call a belief system evil, you transfer that charge to its adherents. You decide to shut down conversation and withhold relationship. You appoint yourself judge of the spiritual and moral value of an entire group of people, people you've never met, and you simultaneously destroy your chances of ever meeting them in trust.

And what exactly do you gain? Moral satisfaction? What do you achieve? More important, what are you hoping to achieve? When you broadcast your belief in the evil nature of a group of people, what are you asking your listeners or readers to do? What are you expecting them to do? Do you want them to be angry alongside you? Do you want them to act somehow to stop the evil? What good do you expect your action to accomplish?