I couldn't understand how these four sentences could constitute a joke, or even a coherent series of statements, until I suddenly solved the puzzle: you're supposed to read the panels in reverse order! Check it out: 'Some opinions are but a grain of sand on the beach. However, in the grand scheme of things… I think everyone is entitled to speak their minds… and that's the way I think we should run this country!' Now all of a sudden there is a logical order of thought -- initial observation, followed by counterpoint, clarification, and conclusion/call to action. The 'joke' is that Herbert is literally experiencing life backwards, yet he has a forward-thinking perspective on the social contract.