I mean, you're not wrong. I don't think it's as simple, and again it's because of AIPAC. Money greatly influences elections in the US, and AIPAC has a bunch of it, while the anti-genocide group coughed up relatively none. Politicians are going to be scared of AIPAC threatening to throw all their money into their opponent's war chests. It's a kind of "hate the game, not the player" situation, except that I don't really believe that slogan: politicians should have stronger ethics. But when it comes down to brass tacks, and you believe that you're going to sacrifice a seat to Republicans by digging in your heels on Gaza because a well-funded special interest group is going to side with your opponent, it's not a black and white decision.
It should be. It should be more simple, but it won't be as long as money plays such an outsized role in politics.