The writing below was for something on the AlwaysLearning list, but I think it's better suited for this. On that list I called it "Christianity and other cults" but neither title is perfect. It's about the integrity of unschooling itself, and a reminder that people should try to see it as separate from any one set of spiritual preferences.
It's not an easy topic. It won't hurt my feelings if everyone ignores it. It helped me to write it out and try to list the angles from which unschooling has been questioned and criticized, or from which people have said "But you're unschooling--don't you also believe X about (morality/TV/plastic/chickens/ecology)?"
Christianity has for years had the most effect on homeschoolers who aren't even Christian, in the U.S. anyway. Ten years ago, they were being told they created, owned and operated homeschooling. It wasn't true, but it was reported with feeling, and with statistics, and one tendency of Christianity is they trust that men of God (however self-proclaimed) are telling the truth.
Lately there are another couple of movements (in the US, and maybe it's more widespread) people have jumped into. They too sometimes (too often) assume that all other unschoolers are coming from that perspective too. One group adopts Marshall Rosenberg's stuff in a religious way and come to consider those don't want to side up with the giraffes or the kangaroos to be heathens (or out of the corner of their minds, categorize them as "violent communicators"). The other group wants desperately to believe in Ester Hicks and her imaginary friend, because if they believe those things they can be rich and happy.
A little older than that and less harsh in the assumptions is formalized paganism.
Waldorf is another set of beliefs that can turn cult-like with some people. The best way to get over that one is to read more and more about Rudolf Steiner. (Or don't get over it, but don't try to cram unschooling into that limited area.)
From the point of view of people who like the idea of being surrounded by powerful spirits and "laws" and who like to feel helplessly placed where they are (or worse, powerfully placed where they are by pre-birth contracts), humanistic ideas of genetics and native intelligence and potential for goodness and plain-old cause and effect without cosmic factors probably can seem irritating.
If unschoolers have other religious or philosophies, that's probably not going to be a problem if their own families can figure out how to prioritize the requirements of the situation. If they believe more in one than the other, that will help them in their decision making. If the two coexist smoothly and easily or they can find a source of assistance to tweak their understanding so that they can do both at once, great!
I know there are people
on this list with fondness for or deep involvement in one or more of those "come and belong to us!" groups. I don't think of humanism as a group, but some people do and have managed to make a minor counter-religion of it, just as some atheists have, with meetings and literature and I guess they have picnics and social stuff.
I'm not trying to talk anybody out of their spiritual preferences. I just want to say to everyone, as I've said to Christians since I first started having to defend my own unschooling on the *Prodigy user group, that people can homeschool without being Christian. People can unschool without having the overlay of another set of rules and justifications. Not all homeschoolers are "pro life" or vegetarian or believers in a pre-birth waiting room, and it should be remembered that not all other unschoolers believe any particular thing about politics or diet or spirituality.
Just as unschooling works the same way for all kinds of kids, it works the same way within all kinds of side-beliefs (or primary beliefs, if that other belief is larger than unschooling in that family), if it will work at all.
Unschooling works when the parents are open and energetic and creative and love their kids without a set of reasons to suspect them and limit them and hold them back. That works not because I said it, and not because there are laws at work in the universe that draw it out to work. It works because of human nature. If people go with human nature instead of against it when they're in the parents-of-young-children phases, the results are way bigger than had ever been suggested in anything I had read when Kirby was little. I've seen it in many other families whose kids are young adults now. We really, truly are onto something wonderful and it works by itself, once you get it working, in normal houses without magic requirements and without special equipment.