We Would Either Need To Endorse Unlimited Harm (such As Killing To Prevent A Scratch), Or An Outright Ban On Harming Others (unable To Scratch To Save A Life). Neither Way Of Rejecting The Idea Seems Morally Plausible. The Idea That Harms - Or Setbacks To People's Interests, Or Infringements Of Their Basic Rights More Broadly - Must Be Proportionate Is Not Only Widely Endorsed, It Crops Up In A Wide Array Of Political, Moral, And Legal Contexts: War, Self-defence, Human Rights Law, Punishment, Free Speech, Political Violence - Basically Any Situation In Which Some Are Made To Bear Costs Which It Would Ordinarily Be Impermissible To Impose, But Which Might Be Made Permissible If Imposing Those Costs Does Enough Good For Others. Since Proportionality Is So Widely Thought To Apply To Such A Wide Range Of Immensely Important Issues, It Is, Of Course, A Hugely Important Concept. Whether An Act Is Proportionate Or Disproportionate Can Be The Difference Between Whether It Is Permissible Or Impermissible To Kill Someone, And Whether (and How) They Are Wronged By That Killing-- Provided By Publisher.