Final answer:
The best example of the cruel jest in Dr. King's 'Why We Can't Wait' is the child's innocent question about racial prejudice. Vivid descriptions of the violence of segregation also exemplify the cruel jest of being told to wait for justice.
Step-by-step explanation:
The excerpt that provides the best example of the cruel jest that Dr. Martin Luther King Jr. refers to in the final paragraph of 'Why We Can't Wait' could be identified within the passage where King speaks about the agonizing pathos of segregation and inequality. An example of such a cruel jest is when a child naively questions the injustices of the world, asking, "Daddy, why do white people treat colored people so mean?" This reflects the innocence and confusion of youth confronted with the harsh realities of racial prejudice, a questioning that King might find emblematic of the immense cruelty embedded within systemic racism and segregation.
Another poignant example is found in the vivid description of suffering under segregation: "...when you have seen vicious mobs lynch your mothers and fathers at will and drown your sisters and brothers at whim; when you have seen hate-filled policemen curse, kick, brutalize, and even kill your black brothers and sisters with impunity..." This passage confronts readers with the violent realities that African Americans faced, and underscores the callousness with which their lives were treated, further illustrating the cruel jest of being told to wait for justice in the face of such brutality.
The ongoing struggle for racial equality and the deep psychological impact of systemic racism are crucial themes in King's writing, which speak to the broader context of the civil rights movement. As King poignantly describes, the mocking of African Americans' dignity and humanity is a stark example of the cruelty he denounces.