Especially if the reverse situation is simply impossible.
The US has a tendency to overreact to threats, but the US military is far more sage and pragmatic than people realize. Iran has the potential to critically destabilize a significant amount of oil flow in the midst of a very shaky global economic recovery. It’s hardly a good idea to test the effects of disrupting a quarter of the world’s oil.
Sorry, people: morality is (and always has been) rarely relevant to geopolitics. It’s always funny to see people express or even hint at moral outrage over these kinds of situations. It’s sort of like getting mad about a cat fighting a mouse.