Disagreement or conflict within a group or church is very common. Those who disagree with someone may have a reason for that. That reason may be unreasonable for somebody else. So the disunity continues. Human beings are in a state of disunity which is evident all over the world.
George Verwer, in his decades of ministry, helped unite many warring factions. He writes on how's and why's of disunity from this wealth of experience.