Meryl Streep as Mother Courage in John Walter’s absorbing, perceptive Theater of War. There are documentaries that entertain and many more that educate, and there are plenty that grab you by the lapels and spout hummus-breath in your face about how you need to stop eating meat and trade your vulgar, barbarous combustion-powered vehicle in for a bike — today! Then there are the rare documentaries that prod you, subtly but insistently, to reexamine the…