Well, I was curious about the voicemail.
At any rate, I live in Italy, and what with the Vatican and all we do have a lot of discussion about how much power should religion have in state affairs. Our school have "religion" as a mandatory subject, and if you don't want your kid to learn about religion you have to explicitly ask for them to be exonerated from attending the class. Now "Religion" can be synonym of "Christianity" or can mean "Story of religions", but in any case, whoever is teaching that subject will always have his or her own views on the matter. Teaching religions in a generic, all-encompassing way is utopian at best. This is one of those topics in which no matter who you are, your views will always be different by those of someone else, and you can't really have no views, because that's a thing, and it goes against those who have a view, any view. It boils down to what you think this world is, where you think it comes from.
So basically you either decide that this stuff should be up to the parents to teach (and I agree with this concept), and leave it out of schools altogether, or you have to choose an angle when teaching it, whatever you find convenient and\or fair. If by "fair" we mean "not mandatory and useful for the majority of people", then I get their point of view. I don't agree with it, but I get it.