I think the point was more that if you wander into a discussion where you already agree with everything being said, your contribution is comparatively less valuable than if you're in a discussion where you disagree.
Perhaps meaning: “Have it your own way, you old buzzard, what do I care!”
Business is built by men who care—care enough to disagree, fight it out to a finish, get facts. When two men always agree, one of them is unnecessary.
- William Wrigley Jr., 1931