Good question, if something like this was a hoax I don't know why they would go the route of a hoax vs. a plant in these situations.
It's not like government in general would be bad, it's just much smaller operations teams that typically work covertly to forward whatever agendas are at play. Think CIA, or one of the numerous other agencies that the public is not privy to.
They run covert operations abroad all the time, so it's not a stretch to consider them running operations at home.
I don't think morality really enters the equation. It's just plan, execute.
But, as far as Sandy hook goes I really don't know. It would really take a thorough, and dispassionate look at the evidence. There is obviously a reason why many people think it is a hoax, so until we really know what evidence that is based on it's really impossible to tell.