What is the purpose of the passage below, and what methods are used to convey that purpose?

Oppressed people cannot remain oppressed forever. The urge for freedom will eventually come. This is what has happened to the American Negro. Something within has reminded him of his birthright of freedom; something without has reminded him that he can gain it. Consciously and unconsciously, he has been swept in by what the Germans call the Zeitgeist, and with his black brothers of Africa and his brown and yellow brothers of Asia, South America, and the Caribbean, he is moving with a sense of cosmic urgency toward the promised land of racial justice. Recognizing this vital urge that has engulfed the Negro community, one should readily understand public demonstrations. The Negro has many pent-up resentments and latent frustrations. He has to get them out. So let him march sometime; let him have his prayer pilgrimages to the city hall; understand why he must have sit- ins and freedom rides. If his repressed emotions do not come out in these nonviolent ways, they will come out in ominous expressions of violence. This is not a threat; it is a fact of history. So I have not said to my people, "Get rid of your discontent." But I have tried to say that this normal and healthy discontent can be channeled through the creative outlet of nonviolent direct action. Now this approach is being dismissed as extremist. I must admit that I was initially disappointed in being so categorized.

But as I continued to think about the matter, I gradually gained a bit of satisfaction from being considered an extremist. Was not Jesus an extremist in love? -- "Love your enemies, bless them that curse you, pray for them that despitefully use you." Was not Amos an extremist for justice? -- "Let justice roll down like waters and righteousness like a mighty stream." Was not Paul an extremist for the gospel of Jesus Christ? -- "I bear in my body the marks of the Lord Jesus." Was not Martin Luther an extremist? -- "Here I stand; I can do no other so help me God." Was not John Bunyan an extremist? -- "I will stay in jail to the end of my days before I make a mockery of my conscience." Was not Abraham Lincoln an extremist? -- "This nation cannot survive half slave and half free." Was not Thomas Jefferson an extremist? -- "We hold these truths to be self-evident, that all men are created equal." So the question is not whether we will be extremist, but what kind of extremists we will be. Will we be extremists for hate, or will we be extremists for love? Will we be extremists for the preservation of injustice, or will we be extremists for the cause of justice?

I had hoped that the white moderate would see this. Maybe I was too optimistic. Maybe I expected too much. I guess I should have realized that few members of a race that has oppressed another race can understand or appreciate the deep groans and passionate yearnings of those that have been oppressed, and still fewer have the vision to see that injustice must be rooted out by strong, persistent, and determined action. I am thankful, however, that some of our white brothers have grasped the meaning of this social revolution and committed themselves to it. They are still all too small in quantity, but they are big in quality. Some, like Ralph McGill, Lillian Smith, Harry Golden, and James Dabbs, have written about our struggle in eloquent, prophetic, and understanding terms. Others have marched with us down nameless streets of the South. They sat in with us at lunch counters and rode in with us on the freedom rides. They have languished in filthy roach-infested jails, suffering the abuse and brutality of angry policemen who see them as "dirty nigger lovers." They, unlike many of their moderate brothers, have recognized the urgency of the moment and sensed the need for powerful "action" antidotes to combat the disease of segregation.

This is the section I was assigned. I see that Dr king uses parellism but dont know exactly why he does it. Need 3 methods that he uses to persuade or convince his readers of his purpose. Also I wrote that his purpose was to "explain how the Negro communites has a new sense of urgency to combat against discriminication" but am not sure if that is right. Please help