Enemies change. At times they’re the ones we don’t like. Other times, they’re the ones who don’t like us. Often an enemy might be a whole group of people, like “those Muslims.” Or it could be those closest to us. Our own family members become our enemies in our worst moments.

This Muslim thing has gotten a bit confusing as of late. It feels easier to know who exactly our enemies are—where they are, and what they’re doing. ISIS is a good example. We feel like we know what they’re up to. They’re clearly evil. They are in the Middle East (or at least we’re hoping they’re “over there”). And they should be stopped. In a sense, that’s the best kind of enemy to have. A clear one.

But this week we experienced one of the confusing “enemy moments.” A white American atheist man executed three Muslims in North Carolina. There have been several other incidents in the last year where American ...