..Or Mormon, or Muslim, or any other religion. They don't know what it is, they can't subscribe to something they know nothing about, regardless of what their parents say.
I 'm not talking about 15 year old children here, I'm talking about 12 month olds, 2 year olds, 4 year olds. There are many children indoctrinated with the religion of their parents.
A metaphor to make this easily understandable would be to compare this situation to calling a child a Republican child, or a Democrat child, or a Communist child. No rational human being would call a 2 year old a republican child. It's ridiculous. They can't understand even the concept of a 2 party political system, let alone pick a side to stand with. If your relative called their 2 year old a Democrat child, you would think it crazy, but somehow calling them a Lutheran child manages to slip by.
Stop labeling children with a religion they don't understand, it's not fair on them, and you sound like an idiot.