David Crosby should be dead. This is not an opinion or a wish, just a plain fact that the iconic rock star readily admits. He used heavy drugs (heroin and cocaine) for years, has had the maximum number of stints placed in his heart, and has diabetes. And yet, while many of his friends sadly passed away due to the unhinged lifestyle they too lived throughout the 70s and 80s, Crosby is still here after all these years at the age of 76, and he’s got some things to say. The wildly compelling and surprisingly emotional documentary David Crosby: …