Reporting from Yosemite National Park— Their Yosemite Valley tour was nearing its end, and the church ladies and gents from South Los Angeles had heard enough. Almost. "He's been telling us stories he thinks we want to hear for two hours," said Ann Hale, 70, heaving a sigh of frustration from the back of the tram. In fact, guide William Fontana had been regaling his listeners — most of them white — with stories about John Muir and Theodore Roosevelt, about fur trappers and rock climbers. "We're still waiting for at least a few words about Yosemite's African American Buffalo...