This with thanks to Stand With US.
Libels are propagated via the social media by anyone who has his own agenda and picks on stories without checking.
Look at the case below. An OXFAM tweeter makes a claim which is followed up by others, only later to realise that there is no truth in the story and a correction is published.
However, as far as Google search engines are concerned the original claim remains. Google still offers the original false claim.