The very best news in today's list of Writers Guild nominees is that Stanley Nelson (right), the writer-director of "Freedom Riders," earned a nomination for best documentary screenplay. Nelson is a master storyteller as well as a superb documentary-maker. He was modest, frank and eloquent when he hosted "Freedom Riders" at the Maryland Film Festival last May. (It also unspooled a few months later at the Chesapeake Film Festival.) But he could have gloated. His film is one of the great social epics of our time. It deserves to win a huge audience when it plays on PBS' "American Experience" in May.