Just a little bit on older kids. If we shut them up so young, they won't feel like sharing later on.
Why do we project on them so much...Wanting to share a philosophy that is important at home? Why not? Kids at 6 will want to share anything about everything, such a nice thing. Open, willing, usually respectful. So, it's the rude "bla bla bla" that I don't like, and, the fact we project a concept of propaganda on a 6yr old and shame them into complete shyness. I do think, culturally, it is important to say to the child, this culture does not invite sharing religious believes in public and one might encounter negative attitudes due all sorts of reasons. Talking nicely about one's believes does not mean in any way trying to persuade, or "steal one's soul", though, it is risky just like any other personal stuff, but at 6, all is personal.
I come from the atheist place in Europe since religion was illegal, pretty much, I would have appreciated if my buddies wanted to share with me their religion and weren't instructed to hide it. Man, I would actually have appreciated if my own religious roots had been revealed to me back then.
But it rubs me the wrong way to haste and say, good, no religious preaching, get used to it, keep it quiet since that is the norm here. Why not let that child decide and trust her own radar to see if she finds good friends who are not afraid of sharing. 6 year olds are usually so eager to philosophy, it is wonderful. Is not a case of sharing because of some kid went through brainwashing. One family teaches some values and passes on some wisdoms, while others pass on something else. Allowing a 6yr old get away with a disrespectful "blablabla" does not really say anything about what steph's daughter wanted to say, rather about what her little friends level of respect and civility is.
I am not a religious bible thumper by any means. But think that the fact that girl wants to exchange ideas is fab. She should be told she might not have people open to her to share theirs and they might not like her views nor appreciate her trying to have an exchange. But, I would be very sensitive about this, since she might find somebody who will want to share thoughts about how this world happened to exist and what is behind things we see. If she decided to quote Plato, we would all aplaude and call her genius. But because she wants to discuss a controversial stuff, we frown.