Be glad that your son will never have to frequent Main Street America and be insulted openly for no reason at all. As horrible as this person's ideologies may appear, we can't not allow even the ignorant to be heard. Kudos to Deanna for bringing up a moral, discerning child. Responsibility falls to the parents to teach children what is right. There would be no freedom if only politically correct speech were allowed.
Freedom of speech is exactly that, a freedom.
The one thing we must remember, just like young Mr. Smith pointed out, there are some people who are going to insist on displaying their bigotry and stupidity. Each of us then has the obligation to recognize such displays for what they are and react accordingly. But instead of airing your complaints to people who can't do anything about it, write a letter or make a call to the school board office or a school board member. Please include your full name and hometown. But alas, we were defeated by the system.