I couldn't find a suitable title for this thread, so resorted to the title of Mark Twain's deeply affecting essay, which I heard on R4 today: Comments on the Massacre of Moro
Another essay that affected me in a similar but different fashion was Orwell's account of Shooting an Elephant.

I don't know what it is that makes writers such as this so expert at elegantly shoving human ugliness in our faces, but they do it in such a way that you cannot but feel responsible at some level for the actions of your fellow beings.

What pieces of literature really compel you to experience the great responsibility being a thinking able human implies in this world.