why did martin luther king jr stress the importance of the gospel of freedom beyond his town?

Martin Luther King Junior was not content with convincing people in his hometown that the rights of black people was integral to the American identity. Like the Apostle Paul, King wanted to carry his message far and wide across the country so everyone could hear the "good news" that America must be a place of true freedom and inclusion of all people.

But more basically, I am in Birmingham because injustice is here. Just as the prophets of the eighth century B.C. left their villages and carried their “thus saith the Lord” far beyond the boundaries of their home towns, and just as the Apostle Paul left his village of Tarsus and carried the gospel of Jesus Christ to the far corners of the Greco-Roman world, so am I. compelled to carry the gospel of freedom beyond my own home town. Like Paul, I must constantly respond to the Macedonian call for aid.