Kennedy said nothing wrong.
In 1963 John F. Kennedy gave a speech in front of the Schoeneberg city hall in Berlin. The speech was supposed to be motivating, because about two years earlier the Berlin wall had been erected. Kennedy gave this speech in English, with an interpreter delivering a German translation. There was however one sentence that was in German: “Ich bin ein Berliner.” And believe it or not, even in 2010 there are English-speaking fellows claiming that this would have meant “I am a jelly doughnut.”
Short version: Wrong. Kennedy was absolutely correct.