As a fan of Heinlein's book, the movie flattened the exploration of the political themes from the book and turned it into said black comedy. It would be like turning Animal House or Lord of the Flies into a black comedy.
I read the book, was very interested by the points he made, but I completely understand and support Verhoeven's take on it as a naive utopia that will get completely derailed. Just look at how the "veterans" of the "forever war" are foaming at the mouth at the idea of war-criming and sending others to die in Iran. Heinlein's central idea that people who offered their service to the rest of society are better qualified to vote doesn't survive the slightest encounter with reality.