Thirty years ago I was a 20-something pastor, green as a sapling, standing in a 100-year-old pulpit dense with ancient oak. Weekly I addressed people who, on average, were 40 years my senior. They were good people, kind and generous. They nurtured me well in my first bumbling years of pastoral ministry. I still feel a deep affection for them and owe them a great debt.

But without anyone even noticing it, we had become a clique. G.K. Chesterton wrote: "The man who lives in a small community lives in a much larger world. He knows much more of the fierce variety and uncompromising divergences of men." We may have been a small community, but we knew little of "fierce variety and uncompromising divergences." What we knew—what marked us out—was sameness and conformity. We attracted people much like ourselves. We felt awkward whenever someone different from us wandered in. And they felt awkward, too—and soon left.

I observed this, but never confronted ...