The term hagioprepēs (ἁγιοπρεπής) derives from the classical Greek root hag-, which denotes something being sanctified as holy or pure. Here, the Greek word hagioprepēs conveys the sense of a person whose actions are highly virtuous. As an exegetical practice, however, "hermeneutical hagioprepēs" is specifically an attempt to minimize, sanitize, omit, justify, or idealize the embarrassing and immoral behavior of fellow religionists (i. e. people who are self-confessed or fully received members of a religious community).
Arguments employed to rationalize saintly sin are often well-articulated by educated, intellectually-minded specialists who present an aura of reasonableness, but only to those who already accept the belief system as true and holy. Attempting to minimize, sanitize, omit, justify, or idealize the immoral acts of both deities and culture heroes, hagioprepēs is ultimately the convergence of Greek allegory, which tried to rescue the reputation of the gods, and ancient apologetics, which desperately sought to make Judaism and Christianity respectable to ancient Greek philosophy. In this sense, hagioprepēs partly derives from a psychological self-distancing tactic that avoids negative thoughts and emotions, which is itself a part of religious cognitive dissonance. Indeed, hagioprepēs appears more designed to assuage the doubts of fellow religionists than it does to justify the outside perception that unethical behavior is widespread within faith communities.
Learn more about the history and philosophy of hagioprepēs in the book, Troubling Topics, Sacred Texts.