Our culture is fiercely committed to relativism. So, when we hear that agreement in truth is a necessary component of Biblical Church Unity, we, as children of our age, feel uncomfortable. Our cultural relativism is challenged by the Word of God on a fundamental level.
Dr. Dilday's Sermon: "In Search of...the Unity of the Church, Part 3: The Challenge of Relativism"
https://www.sermonaudio.com/sermoninfo.asp?SID=130221628433931
Other Sermons in "In Search of...Church Unity": https://www.fromreformationtoreformation.com/blog/categories/church-unity