I can think of a few reasons why this is true for the church (for the record, when I refer to diversity I mean race, age, education, socioeconomic, etc):
- The more the people around you are just like you, the less likely their opinions and views on life will contradict yours. This is another form of individualism that can lead to big problems because it will cause you to live life with huge blind spots and sin in your life gets more difficult to spot.
- Creativity is stifled. If you're all the same, it's difficult for new ideas to emerge that make long-term sustainability possible (just ask GM). Without fresh ideas and perspectives, you end up doing the same old, same old, which gets outdated quickly.
- Bringing people together who are different is at the very heart of the gospel. Simply put, sin separates, but it's the gospel that brings us together. The gospel wants to bring everyone together from every tribe and tongue, from every nation, and from every generation. If in your church, everyone is the same, it could indicate that you have a gospel problem. If you have a gospel problem, you won't have a church for very long.