Governmental or judicial issues are always going to be inherently political. I think instead of trying to prohibit "political" discussions, it may be better to try and restrict explicitly "ideological" arguments.
Anyway, I think one of the government's primary roles is to protect people from others, when they are in no position to protect themselves. This is a perfect example of that. The Constitution and Supreme Court have essentially said that people with religious or other views that depart from the mainstream have a right to think whatever they want, but they can't act as their beliefs suggest if it either impinges on the rights of others (presumably including their childrens' rights to a healthy life) or in some way undercuts their adherence to the "national identity" (thus, they have to pay taxes, respect existing laws, etc.).
