Letterman might've been trying to make funny but it was a decent interview considering that show. Jones came across just fine and i have to give credit to Letterman to have someone like this on.
Jones is still one of the top few gurus ever in BB along with Gironda. Weider tried to discredit him in the 70s but it didn't really work. His influence remains thru the Hammer Strength equipment that's in virtually every gym these days, as well as the idea of less frequent workouts that most use now that was considered radical back in the volume days. It's true that most guys don't use HIT because to do it correctly is gruelling and unsatisfying to those who like to spend more time in the gym.