In case you’re implying the parent should also provide evidence: it’s way harder to prove the non-existence of something than the existence. I’m not sure if that’s a universal rule (in math for instance) but it’s certainly in something like a magic teapot behind mars.
I do think the strength of evidence should be somewhat correlated to the weight of claims,
Maybe a sidenote to extraordinary claims require extraordinary evidence. I've expressed similar sentiment here https://news.ycombinator.com/item?id=17738147