This is not the way to think about them. Terrorists are human. They had the choice to be good people. THEY CHOSE EVIL. They are still human. I think it's wrong to call anyone not human. We don't need to dehumanize terrorists to capture and kill them. We do so because they brought us to war and they are our enemy and they must be stopped from their evil.
You beat me to it. Exactly right. We cannot so simply write terrorists off as "not human". They are very much human, who have chosen evil ideologies over goodness.
Heck, they could have even chose ambivalent and still been OK. But no, they chose evil.