If Kanye had phrased his rant like this, he would have been using parallel structure:

Now, I'm not saying that you didn't deserve this award, but I am saying that Beyoncé had one of the greatest videos of all time.

Parallel structure is a fancy way of describing repeating syntax. When using parallel structure, a speaker repeats combinations of words, sentence patterns, or grammatical constructions. "I'm not saying," but "I am saying" is an example of two phrases with identical syntax.

A great example from "I Have a Dream" is "to work together, to pray together, to struggle together" (18.5). The words aren't exactly the same, but the construction, or pattern, is the same. In the very last paragraph, King says, "when this happens, and when we allow freedom to ring, when we let it ring from every village and every hamlet…" etc. (21.1). Here, the repetition is tight enough for the audience follow along, but loose enough so that it doesn't seem totally pedantic or boring.

Repetition lets the themes of a section sink into the audience's head. In these examples, it's faith, aspirations, and the Civil Rights Movement's general goals. Remember, if you say something the same way enough times, eventually people will be engaged, and maybe even believe you.

Oh, and don't forget. The whole "I have a dream" thing is also an example of parallelism as well. One paragraph after another is constructed in the same way. It's a sweet method of driving home the message of the dream.

With this MLK was a great speaker, and with this the audience listened, and with this sentence we're giving you another example of parallel structure.