Earlier quoted context omitted.
This is a bit Pollyanna. People aren't logic robots that start from first principles and then derive all knowledge from logical reasoning. People are emotional, irrational beings. Those of us who fancy ourselves rational are constantly involved in irrational motivated reasoning helping us maintain that desired worldview. Not to say we shouldn't try to live up to the ideal you set forth. We should do our best. But the…
People are not robots, but in terms of reaching agreement between humans, "emotion" is more or less just a difference in priorities, which is one of the ways reasonable people can disagree. If we agree on the facts and we agree on their implications, but we still disagree, it's likely because we weight things differently. Emotions are simply a large component for how we weight things.
Even mature people often can't reason their way out of a conflict on their own. When people feel personally threatened, sometimes no amount of simple reasoning will bring them back to rational thinking. Most of the time, the solution is to be a genuine friend--for the long haul.