Imagine if our courts were uncomfortable with conflict. Imagine if--to avoid conflict--they didn't give everyone a chance to present their side of the story, to disagree with each other, to get emotional and confrontational. Imagine if the judge and jury only heard one from one side--maybe just the prosecutor--before declaring a verdict and a sentence.
Chip and Dan Heath make this powerful example early in their book Decisive-How to Make Better Choices in Life and Work to illustrate one of the key requirements of good decision making: seek out a variety of viewpoints before making a decision. They say that the quality of your process for seeking out different points of view is more important than the quality of your THINKING! How logical you are, how analytical, how clever--none of that matters if you don't make sure that people with different points of view get a chance to speak their minds.
So this is another reason we should be happy when other people disagree with us, when other members of the group have different ideas. Just as we expect our courts to give all sides a hearing because we know that this increases the odds of a good decision, we should welcome conflict and objections to our points of view at home or at work.