I agree with Gideon Sylvester that the behavior depicted in the youtube video clip from the Yom Yerushalayim march is detestable and must be condemned. However, before we decide to boycott the Yom Yerushalayim marches, a few things need to be kept in mind:
The vast majority of marchers (at least during the daytime Rikudegalim flag dance march which was depicted in the video) do not engage in this type of behavior. Although I was not there this personally year, my students were, and they confirmed what I have witnessed myself in previous years: the program is an excellent, well-run celebration which all Jews should be proud participating in. The vast majority of the marchers do not issue any political statements at all, and certainly do not act offensively. It is not fair to judge an entire event with thousands of participants on the basis of a carefully edited video clip.
Although the behavior depicted can certainly be called vile, I saw no evidence of violent behavior. Furthermore, almost none of the slogans could be called racist either (the expression kill the Arabs at the end was a notable exception and, in fact racist but the other slogans were not). When our opponents use hyperbole to criticize Israeli policies (for example, the expression apartheid state), we justifiably protest. Let us not be guilty of the same offense ourselves.
Provocations are a 2-way street. The clip begins with pictures of Arabs flying Palestinian flags on a rooftop in Jerusalem, Israels sovereign capital. This behavior which is a criminal offense in many countries including the United States must also be condemned. Why the Israeli police did nothing to stop this is beyond me, and it certainly does not justify the unfortunate reaction of the Jewish teens filmed, but the context of these reactions cannot be completely ignored either.