Ahh, dueling sources! Here's a couple arguing for DDB having made the ad:
Maybe it was Moyers' idea, but it was the ad agency you cited which produced it. At any rate, it was axed after one showing. Goldwater said that Moyers made him puke when he saw the Marshall, TX, native on public television. Goldwater also declared Robert Strange McNamara and Richard Milhous Nixon as the most dishonest men that he ever encountered in public life. Of course, Goldwater had thrice supported Nixon for president before he issued his warning.