When MacArthur said, “There is no substitute for victory”, he was not trying to quip or to merely stress importance; he literally meant that there was an existential threat to the American way of life and that no alternative other than complete Allied victory would suffice. There was no solace or consolation in any other outcome that could ever approach being a substitute for the continuation of our lifestyle and values.
While not everyone will face the bloody truths and clarity of war, many good people find themselves in personal situations where anything other than complete exoneration would mean disastrous ruin. The man falsely accused of a crime; the woman facing politically motivated professional misconduct allegations; the student railroaded into expulsion proceedings by the university.
There are times in life where we cannot choose to leave rounds in pocket, in magazine, or even in chamber. When the threat will stop at nothing to defeat you, when a force cannot be simply discouraged or ignored, you need to bring every weapon at your disposal to stop it. If your value and legacy are irreparably damaged, what good is spare ammo but to serve as a reminder that when forces clashed, you stopped short of fighting with everything you could?