I honestly think that the practice of demanding a source or a claim is instantly invalid is a bad one. If I make a claim, it’s because at some point I wanted to know the answer to something, so I looked it up. Or, I didn’t believe a claim someone else made.
It’s a mistake to trust some stranger on the internet to provide an unbiased source that wasn’t cherry picked to support their position.
Plus, most sources can be found with a <5 word Google search.