Millions of Americans were stunned and incredulous on Monday after learning of a possible incident of bias at Fox News Channel. At a time when so many American institutions have been under attack, the possibility that Fox, one of the nation’s most respected news organizations, might be susceptible to hidden agendas was too much for many to take. In interviews across the country, Fox viewers expressed disappointment, confusion, and shock that a news network known for its exacting standards had imperilled its hard-earned reputation for fairness.