When a person is in conflict, they will frequently seek out others to provide counsel and guidance. If someone in conflict comes to you, then you will be getting one side of the story and it is easy to get drawn into the corner of the person you are speaking with.
But, peacemakers are not in one person's corner or the other, but rather in God's corner which is the corner advocating for a healthy resolution of the conflict. So, it is important to be a wise counsel, understand that you are only getting one side of the story, and remain impartial.