Synthesis theory: They would kill us whether or not we killed them, but they kill us more because we killed them.But I would supplement this with one of my own:
Scapegoat theory: They want to kill people because of their lousy economic circumstances, which result from their zero-sum non-capitalist economies. They kill us because we're rich, and thus we provide a convenient scapegoat.How can Scapegoat theory be included in the Synthesis? There are lots of scapegoats to choose from, so they target the nation that is richest and most meddlesome. If we reduced our meddling, they would still want to kill us because we're rich. But not quite as much.