I never said what material the teapot was made out of
Dark matter. ITS ALL TEAPOTS.
I'm not going to go out of my way to prove that fairies and wizards don't exist (I consider this a waste of my time, just as I do with regards God) without a situation in which that believe is actually being problematic.
I would argue that beliefs such as religions* are inherently harmful independently of their actual content. Religions can convey very good ideas or very bad ideas, but the thing they have in common is
how they convey them. That common trait is revelatory faith, which is completely unaccountable. No matter how contrary an idea is to evidence or logic, to a true believer it
doesn't matter because they received it directly from their god**. Unreasonable and unshakable convictions are hardly unique to religion, but religion is different in that it asserts that you don't
need a reason if you have faith.
Why is this a problem, some might ask, when religions can promote good ideas as easily as bad ideas?
This is a problem because religious belief itself contains much more than the actual content of the relevant holy books. A religion's scriptures are relevant, but in a person's actual beliefs they are heavily modified or even supplanted altogether by a number of unconscious factors such as culture and emotions.*** These factors effect everyone's beliefs about life, religious or otherwise, but religion adds one more layer of resistance to change. This effect allows
any belief to potentially be considered beyond (or less susceptible to in milder cases) to questioning and reason, which tend to favor good ideas over bad ideas (if only because many bad ideas are illogical or rely on provably false premises).
My argument in short is that religion promotes ideas more or less indiscriminately, which makes it easier for bad ideas to stand against good ideas despite being bad ideas.
* In this post, by 'religions' I mean gnostic religions.
** Many or arguably most followers of religions rarely take things to such an extreme extent, but this effect is much more common in more subtle forms.
*** For example, numerous wealthy people such as bankers believe in and support Christianity, which explicitly condemns wealth and money-lending.