The problem is that if religion is explained to children in the context of "some people believe this," and then they ask, "but is it true?" you're forced to say:
1) "No." Which is the truth as it is observable in the real world, but again, not popular. 2) "Yes." Which is an opinion at best, a lie at worst. 3) "It's what some people believe," which is no kind of answer, and in the process sets the stage for kids to believe that whatever they believe is not only right but true.
no subject
The problem is that if religion is explained to children in the context of "some people believe this," and then they ask, "but is it true?" you're forced to say:
1) "No." Which is the truth as it is observable in the real world, but again, not popular.
2) "Yes." Which is an opinion at best, a lie at worst.
3) "It's what some people believe," which is no kind of answer, and in the process sets the stage for kids to believe that whatever they believe is not only right but true.