Here’s a clip from Dick Cavett’s Vietnam (PBS, 4.27. 10 pm), a 60-minute doc by John Scheinfeld. It blends a brief overview of the Vietnam War, discussions of that quagmire by guests on The Dick Cavett Show (John Kerry, Warren Beatty, I.F. Stone, Sen. Barry Goldwater, Daniel Ellsberg, Woody Allen, Jane Fonda, Vietnam veteran John Mueller, Sen. Wayne Morse, etc.) and some present-day hindsight from Cavett, Gen. Wesley Clark and historians Timothy Naftali and Fredric Logevall. It’s stirring, angering, well-ordered time travel — brings it all back. I only wish PBS had commissioned a two-hour show.