Whatever you think about Michael Moore and his movies, one has to admit that the marketing materials for them have been excellent. And these posters for Sicko are no different.
The general design is one that we have seen before in the Fahrenheit 9/11 poster: Michael Moore + some comic elements + clear references to a controversial topic. I think that the poster below is a little funnier, however, the one above is more iconic and memorable. But they both probably do a great job of getting the core audience for the movie excited about it.
Preaching to the converted? Maybe, but it will sell tickets.