Urmstongran, this is not about sex (again!). It is about equality and how we treat people in an inclusive way. None of the books, etc., that I have seen are anything other than age appropriate. I think maryeliza54 is right - what do you mean by "all this"?
Aristotle said, “Give me a child until he is 7 and I will show you the man.”. The Jesuits later took this up because they knew it to be true. If we want to have children that grow up without the prejudices some, even on here, seem to hold, we need to get the message over as early as possible.