Final answer:
Martin Luther King Jr. identified the 'white moderate' as a significant obstacle in the civil rights movement because they preferred order over justice and were hesitant to support the urgency and direct actions needed for real change.
Step-by-step explanation:
According to Martin Luther King in "Letter from Birmingham Jail," he had almost concluded that the Negro's great stumbling block in the stride toward freedom is not the outright extremist like the Ku Klux Klan member but the white moderate.
The white moderate, he explains, is more dedicated to 'order' than to justice, preferring a negative peace, which is merely the absence of tension, over a positive peace, characterized by the presence of justice. King believed that this priority of order over justice by the white moderates was a significant barrier to achieving civil rights as they were often hesitant to support direct action and the urgency of the movement.
King's letter highlights the frustration with the slow pace of civil rights progress and criticizes the white religious leaders for their passive approach. He longed for them to advocate for integration not merely as adherence to the law, but because it is morally right. Consequently, King's profound disappointment in the white moderate's preference for tranquility and the status quo over substantive equality contributed to the civil rights struggles.