Utilizing moral foundation theory (MFT), this study posits that observers' acceptance of unethical pro-organizational behavior (UPB) aligns with their inclination towards loyalty or fairness values. Furthermore, it contends that observers' personal acceptance shapes their perception of peers' UPB endorsement, thereby influencing their pro-organizational and quiescence silence. A two-phased vignette-based field survey involving 292 working individuals in the USA was conducted to test these hypotheses. The results reveal that observers' preference for loyalty over fairness moderates their personal acceptance of UPB and influences the perceived peers' UPB acceptance. This distinction in moral preference leads to the manifestation of distinct biases, such as false consensus or uniqueness bias. Loyalty-preferring observers exhibit a false consensus bias, while fairness-preferring observers demonstrate a uniqueness bias. Importantly, this study illuminates the intricate nature of UPB observer behavior, demonstrating that loyalty-preferring UPB observers are more likely to maintain pro-organizational silences, while fairness-preferring UPB observers are inclined towards quiescence silence. In essence, the study uniquely contributes by delineating how varying moral preferences among UPB observers give rise to divergent biases, elucidating the complex motivations driving their choices to maintain silence.
