The previous moon thing is a joke and at least partially an explanation for "freedom units," which is a joking (I think) commentary about the citizenry's belief

The previous moon thing is a joke and at least partially an explanation for "freedom units," which is a joking (I think) commentary about the citizenry's beliefs about "their freedoms," and somehow these freedoms translates to freedom from using the metric system when they roll coal along a couple furlongs of interstate (in a truck that contains only metric fasteners.)