Self-contempt is the core psychological cost driving people to rationalize

Evidence

In conflicts of greater moral weight, there is no more devastating consequence than self-contempt. If the allure of rewards or social pressures outweigh self-censure for personally devalued actions, the result can be cheerless accommodation or disillusionment and cynicism about one’s activities. However, people figure out ways to mitigate the costs of self-devaluation. — Albert Bandura, Moral Disengagement, 111

Categorization

• corroborated: 2 independent passages support this claim — Albert Bandura, Moral Disengagement: How People Do Harm…, 111
• XREF: connects to: Daily exposure to adversarial argument can convert contempt into grudging respect. — , Harr Jonathan - A Civil Action , 1863