I doubt that the judge was ruling that the words themselves are not offensive. Nor was the judge likely ruling that the words are not indicative of someone who is profoundly anti-semitic. Rather, the judge was likely ruling that a particular crime of anti-semitism had not been committed. Often crimes of that sort require words to be uttered or acts to be carried out with a specific intent of expressing hatred towards Jews. What the judge likely found is that, despite the fact that the words are indicative of a hatred towards Jews, they were not uttered with the intent of expressing hatred towards Jews, but rather of "defaming" the other team. Of course, it is profoundly anti-semitic to think you can "defame" someone by calling them a Jew--but if there is a specific intent requirement, it is hard to argue with the fact that the intent is to defame the person you are addressing, and not Jews. By the way, we'd probably have the same result as this Polish case under US hate speech laws.
from the article: Polish prosecutor: 'Jews to Auschwitz’ chant not anti-Semitic