Self-Justification

We live by certain set principles and self-imposed or learned guidelines. We do not want to move astray from them. In ordinary situation at least. However, whenever a situation arises when we have to move away from the set track, we try to justify our detour through various logical arguments or points. This way of convincing ourselves that our detour, though not justifiable with respect to our own set standards, can be justified as a special case. We try to garner facts, arguments and notions in favor of the detour and make the belief stronger that the detour is for the better. Or we convince ourselves that we shall be better off if we take this exception. This is a well-known and much debated act of self-justification.

When Yudhisthir told a lie for the first time to convince Drona that his son Ashwatthama had perished in the war of Mahabharata, he convinced, though reluctantly and goaded in by Krishna, that he was telling the lie to attain victory for the good cause.

Revolutionaries waging so called fight for the poor justify violence and atrocities against the same populace by arguing that some violence is inevitable in a war to achieve a greater good. Striking employees justify disruptive actions showing their goal of greater good. A driver justifies his breach of road etiquete by putting forward a case of haste or lapse of judgement.
https://www.pcc.edu/staff/pdf/602/Chapter5Self-JustificationPPT.pdf