Facts are everything for engineers, whether they be computer science, mechanical, electrical, or civil. In a utopia of engineers, there would be no disagreements. All decisions would be made by coolly laying out the comparison criteria, assessing the different options, comparing the facts, and picking the obviously logical choice. Sadly, this world does not exist (no matter how hard you wish for it).
Opinions, Perceptions, Personalities, Politics, Emotions. These are the qualities which drive decisions whenever more than a single person is involved. And anyone who has a grasp of these items and can use them skillfully will easily outmaneuver someone who only has the facts on their side but is ignorant of these items.
To be successful, you need to understand when it is appropriate to discuss facts and when the facts are irrelevant and the issue at hand is perception. This came up recently in a meeting I had with a client where they were evaluating our performance. There was a criticism of our company which, if one only looks at the facts of the situation, we were in the right. However, our attitude and reaction to the situation resulted in a negative opinion of us as an organization. In such a situation, continuing to argue the facts of the matter results in a reinforcement of the negative opinion (sadly, one of our people fell into this trap). The proper reaction was to accept the criticism and address the perception problem while simultaneously organizing other forums that are fact based to address the inaccuracies there.
Being a good engineer requires you understand and can apply the facts of your trade. Becoming a great engineer requires that you must understand that people are not neat and pretty and definable through equations and logic.