Really? I do not think it means what you think it means.
Man·i·chae·an noun \ˌma-nə-ˈkē-ən\\ˈma-nə-ˌkē\
1: a believer in a syncretistic religious dualism originating in Persia in the third century a.d. and teaching the release of the spirit from matter through asceticism
2: a believer in religious or philosophical dualism
It’s the dualistic thing they’re latching onto, and though Manicheanism means more than that, it’s become a standard ancient reference, like Philistinism. Bush the Younger did say something about “you’re either with us or you’re with the terrorists” shortly after 9/11 to Congress, so there’s some justice to it. Of course, you could impute the same dualism to Obama, Clinton, Carter, or most any modern leader. Because that’s how we talk now. We don’t say you’ve stained my honor or I want your stuff. We say you’re evil and we’re the force of light.
In my experience, modern usage of “Manichean” means arbitrarily judging every person or event as good or evil, without any possibility of compromise.
And, in my historical judgment, it’s the only way to fight a successful war.