Should we police flat-Earthers?

They seem to so desperately want the world to be flat that they will come up with any argument that whatever conclusively disproving new evidence they just looked at to prove their idea was somehow manipulated or in some other way confounded.

Surely when others hear their sincerely delivered explanations some will also conclude that the world is flat.

Is there a cost-benefit analysis we should perform here?

What are the costs and benefits of policing misinformation about other subjects?