The correct answer to this open question is the following.
The words with strongly positive connotations that King uses in lines 13-539 are the following: Dr. King uses parallelism, loaded language, and rhetorical questions.
His use of this loaded language is an effective way to end the speech because this kind of language produces an emotional response in the audience, and that is what Dr. King wanted to provoke in his audience. An emotive response, to persuade and appeal to the emotion of the public. In his speech on the War of Vietnam, he is using pathos, the appeal to the emotion of the audience to convince it.
