In theology, John Calvin and Jacob Arminius were not that far apart on many things. But on one issue they disagreed. In that disagreement, in order to explain and argue their side, they pushed each other further and further from the center. Neither becoming more right or more wrong, but just more opposite and further from center in their arguments against each other.
A similar thing happens here often. You and Mr Sensible may be one inch left of center and one inch right of center, respectively. But as you make your "1 inch right of center" comment, the guy on the other side feels he need to go 2 inches left of center to offset you. Then you (not literally you) go 3 inches right to counteract his two inches left.
Pretty soon there is a fight where one side appears 20 feet left of center and the other 20 feet right of center....when in reality, there is much both sides could agree on in regards to the other sides stance, which is why the argument started only two inches apart....each side one inch from center.