What is King's argument?

In The Letter from Birmingham Jail, King notes the reason for his presence in Birmingham, “I am here because injustice is here.” His three reasons for being in Birmingham include the fact that he is president of the Southern Christian Leadership Conference, and that he was invited by the Alabama chapter. He then compares the SCLC to 8th century prophets, who carried the word of Jesus far away from their homes, and he goes on to compare himself to Paul of Tarsus, who brought the gospel to “the far corners of the Greco-Roman world.” Dr. King is attempting to carry “the gospel of freedom” to areas far and wide (170). Lastly, King argues that “all communities and states” are interrelated, and as a just man, he cannot ignore injustice merely because it occurs outside of his hometown. “Injustice anywhere is a threat to justice everywhere,” since everyone feels the sting of injustice, even if indirectly. As a result, nobody in the United States should ever be considered an outsider anywhere else in the country (170).