I think I agree that uploaders face more of a threat from censorious activists reviewing their old material than they do from retroactive deletion prompted by YouTube policy changes, but surely self-hosting would provide some protection, assuming the audience would be willing and able to transition to a different source?

It seems to me that hosting and payment processing companies ultimately present the greater service denial risk for uploaders with an established audience, though YouTube can definitely hamper new viewer discovery, and there is more competition (and therefore more alternatives) in hosting and payments.