The enemy here is not "multiculturalism", and it is wrong of Garvin to argue that the point is that U.S. courts now favor Hispanic bullies over (presumably) white loudmouths. The real lesson is that U.S. students have systematically been stripped of the rights due U.S. citizens, so that the courts no longer have recourse to protect them against arbitrary decisions by school administrators.
The Supreme Court case mentioned as precedent dates from 1969, but Garvin doesn't bother to think about the context... Hm, 1969, any guesses as to what the case might have involved? It was about students wearing black armbands to protest the Vietnam War.. In fact the decision permitted such displays, but carved out an exception if speech would "materially and substantially interfere with the requirements of appropriate discipline in the operation of the school." And that, as Mr. Garvin has just discovered to his horror, is an exception wide enough to drive a truck through.