Political Science Epigrams
If your policy is, "We don't negotiate with terrorists, but we do appease bears", then from the perspective of a third party fighting a war against the bears, you look like a productive asset being farmed by the bears, and thus, a legitimate military target.
If your behavior is optimized to respond to political threats, but not to small requests from your friends, at some point your friends start to face a strong incentive to stop being your friends and start threatening you politically, because you've made it clear from your behavior that that's all you respond to.
If you were angry at an enemy (who used to be a friend), you might throw a rock at them. But if they didn't react to the last rock, you need to patiently build a bigger rock.