I believe in free speech, but when it comes to claims like this which are clearly untrue, it would seem to me the government would have a duty to prosecute for misleading the public.
In the case of a disaster situation, it could cause panic and harm to those living in the disaster region.
When the only motivating factor would be political, it’s simply not in the nation’s interest to allow this type of thing.
Under certain circumstances, I don’t think a fine would be enough either. They should serve prison time.
I think you are right; a case could be made for criminally prosecuting Krugman. I hope this is done and even if the govt loses; hopefully, it will cost Krugman so much money, every journalist will think twice before they lie. Also, I wonder if this tweet could be considered an act of terrorism?