First things first: what the anaphora is an anaphora? Easy-peasy lemon breezy: it's the repetition of phrases at the beginning of clauses. (Think: "It was the best of times, it was the worst of times.")

And sentences 6-14 in the "Ich bin ein Berliner" speech form a repetitive pattern. Kennedy starts each with an acknowledgement of counter-arguments. Each is the perspective of someone who doesn't think communism is all that bad and begins with the words "There are…" After each of these he redirects by saying, "Let them come to Berlin" as a simple, yet effective way of proving them wrong:

There are many people in the world who really don't understand, or say they don't, what is the great issue between the free world and the Communist world. Let them come to Berlin. There are some who say that communism is the wave of the future. Let them come to Berlin. And there are some who say in Europe and elsewhere we can work with the Communists. Let them come to Berlin. And there are even a few who say that it is true that communism is an evil system, but it permits us to make economic progress. Lass' sic nach Berlin kommen. Let them come to Berlin. (6-14)

This anaphora repeats four times with the final, "Let them come to Berlin," also spoken in German. It's an effective way to silence criticism without spending a lot of time and energy acknowledging your opponent.

Have you ever been in an argument that feels like it's going in circles and you're getting nowhere? That's basically what the Cold War was like. Instead of a boring dissertation on the many flaws and misconceptions about communism—which would just be rebutted with a similar yawn-fest about capitalism—Kennedy just repeats one solid point over and over.