At a clergy seminar on Catholic-Jewish relations I attended recently, Catholic scholar Philip A. Cunningham  reminded us that Jews and Christians haven't been in serious, respectful dialogue for very long.
Indeed, this important effort has lasted but a tick of the clock compared with the century after century of anti-Judaism  preached from the church almost from the beginning of the Jesus Movement within Judaism in the first century.
As I have studied and written about this lamentable history in recent years, I have wondered again and again why we seem to need to put ourselves on a pedestal from which we wield a sword against people racially, ethnically or religiously different from us, people we call degenerate, disgraceful, unorthodox.
The late Felix Zandman, a brilliant Holocaust survivor I wrote about in my last book , once told me he believed it was because people doing the oppressing fear they may be wrong, so they crush those who might enlighten them about their errors.
I like that theory. But I also was taken by another theory I heard recently from a man many Christians -- perhaps out of fear of "the other" -- have labeled a heretic, Episcopal Bishop John Shelby Spong .
Spong said we put others in separate boxes because of our survival instincts.
"It is out of need and desire to survive," he said in a lecture I attended, "that we will do every evil imaginable. That's why we human beings build ourselves up by tearing other people down.
"That's where prejudice originates. That's where xenophobia is born. That's where religious bigotry comes into being. That's where we get religious persecution and religious wars and religious intolerance. ... That's why the more religious people become, so often the meaner they become. There is no war like a religious war. There is no fight like a church fight or an interreligious fight."
No doubt all of us have experienced this in various ways. When I was in high school, for instance, the pastor of my hometown Presbyterian church  warned our congregation that if John F. Kennedy were elected president, the pope would move to the United States and run the country.
It was classic us-vs.-them religious bigotry. And I was by then wise enough to recognize it because I'd had the opportunity to live with my family for two years in India and had gotten to know Hindus, Muslims, Sikhs, Jains and others who might well have represented the dreaded "other" to me had I not been able to look them in the eye and see that they were just as human as I was.
Religious warfare, of course, occurs not just between people of different faiths but among people of the same faith. So we find anti-Catholic rhetoric still among some Protestants. But, maybe worse, we find Catholics, Protestants and Orthodox Christians divided internally in ways that must break the sacred heart of Jesus.
It's happening now in my own Presbyterian denomination  because we have changed our constitution to allow for the ordination of otherwise-qualified gays and lesbians. It's happening also in the Catholic church over such issues as ordination of females, abortion rights and responses to the priest abuse scandal.
My friend Kathleen Norris  says in one of her wonderful books that we Presbyterians (she's one) get especially vicious in our fights when the subject is the church holy of holies -- the church kitchen.
I'm not sure we'll ever get rid of what Zandman called the fear of being wrong or what Spong called our myopic survival instinct. But I think we can get closer to moving beyond those factors if somehow we can remember that Jesus came so we might have life, and have it abundantly.
And surely part of what Jesus meant is that we should respect and honor the life of others even as we seek to be fully human ourselves.
[Bill Tammeus, a Presbyterian elder and former award-winning Faith columnist for The Kansas City Star, writes the daily "Faith Matters" blog  for The Star's website and a monthly column for The Presbyterian Outlook. His latest book, co-authored with Rabbi Jacques Cukierkorn, is They Were Just People: Stories of Rescue in Poland During the Holocaust . Email him at firstname.lastname@example.org.]