I think it's less about lowering the listener's defenses to the idea so that they're easily persuaded, and more about giving them the impression that they're actually learning something of substance, when they're actually not. In a week they'll be completely unable to articulate any of the important ideas from the talk, not because it's a poor learning style, but because there were never any important ideas to begin with. "You just have to watch it." It's like thought junk food. It's instantaneously satisfying but provides no actual mental nutrition.