We gave up when we went on Twitter to see just how much nonsense was floating around and realizing that even basic lies took 30 minutes each to refute. Assuming that we had perfect access to people's information feeds and assuming they all believed us anyway (and many wouldn't), we would still need 6x as many people as popular trolls/liars existed to fight back.
You would basically need to have a legion of volunteers willing to spend 30 minutes undoing 5 minutes of damage.