I think the objection here is that it creates a massive loophole: Intentionally post misinformation, claim you thought it was legitimate. Repeat until you stop getting the benefit of the doubt, start over with a new account, repeat ad infinitum.
I'm not sure what the best solution is, but I think we at least need some kind of very clear notice, on the feed page and not just in the comments, that the content is proven to be factually incorrect.