Treason is a deliberate violation of fidelity to someone or failure to perform a debt. The betraying person feels shame and repentance, and then either tries to correct his act and copes with it, or seeks an excuse. Why make excuses by deceiving yourself? Many writers tried to answer this question. I think, because each of us wants to feel right in all cases of life.
Erast, the hero of the story N.M. Karamzin's "Poor Lisa", betrayed the feelings of his beloved. Lisa surrendered to him wholeheartedly, but after losing the novelty in the relationship, the girl got bored with the hero. Erast decided to leave her, but could not even say so directly, referred to the draft in the army, explaining the separation. The hero decides to marry another woman by calculation, he betrays the pure soul of Lisa, tramples her feelings. Of course, he is justified by a mesalliance (like a nobleman being with a peasant woman), difficult life circumstances, but in fact he is weak. This weakness led the heroine to death, and the torment of conscience of the hero can not dispel any excuse.
Together with Andrei Sokolov, the hero of the story M.A. Sholokhov "The fate of man", the reader observes betrayal in the war, which means not only the betrayal of individuals, but also the homeland. During the drive of the prisoners, a night stop was made, during which Sokolov heard a conversation between a soldier and his former commissar. The soldier was about to extradite a political worker who would inevitably be brutally killed. The traitor is justified by his hatred of the party and the instinct of self-preservation. But he would have killed with his own hands a man who had not done him anything wrong, and if everyone had done so, he would have split up and could not stand against the enemy. However, Sokolov was also outraged by the cowardly meanness and killed him. This murder may have saved many lives, not just the fate of one commissioner.
Thus, one can always find an excuse for his meanness in order to maintain a reputation. But this can be a deceit for others, and not for oneself. And the whole life of the betrayer will be poisoned by remorse, so you need to try to do everything to prevent betrayal, not to waste your energy looking for excuses.
