That's actually an easy question to answer. All too often, getting it wrong has also been a Christian tradition.
Throughout the ages, various Christian beliefs have been the basis for institutions and actions that were anything but Christian. The Inquisition and the Crusades come immediately to mind, but more recent history also has its share.
For many centuries, "good" Christians used the Bible as a basis to deny women basic human and civil rights, to imply that handicapped people must have sinned to deserve their disability, and to justify anti-Semitism.
It wasn't until the late 1700s that Christians began to seriously question the morality of slavery. When the U.S. finally abolished slavery in 1865, many sincere Christians still believed it was a valid state for black people, and found biblical "justifications" to back it up. As a result, some Christian colleges in the South continued to bar people of color from attending through the 1960s and '70s.
Interracial dating, too, was considered taboo for many years because of certain Bible passages. In 1967, the U.S. Supreme Court finally struck down the last of the state laws banning interracial marriage, but it wasn't until March 2000 that the "biblically faithful" Bob Jones University lifted its ban against interracial dating.
History has shown that harmful beliefs will continue until people begin to question them, even in the church. And the questioning is always controversial at first.
We didn't begin questioning society's prejudice against homosexuality until UCLA psychologist Evelyn Hooker first began examining it in the 1950s. In 1957, Hooker's research concluded that "homosexuals were not inherently abnormal and that there was no difference between homosexual and heterosexual men in terms of pathology."
There have been many studies since then, and, in 1973, the American Psychiatric Association deleted homosexuality from the list of sexual deviances. All major professional psychiatric, medical, psychological and educational organizations have followed suit, based on myriad studies that have confirmed Hooker's initial findings for gay individuals, and more recently, gay families.
Traditions die hard, however, especially in religion. There are only three verses that deal with homosexuality in the New Testament, and many New Testament Greek scholars would argue that those three verses don't deal with homosexuality as we define it today, but rather with temple prostitution and other abuses. Unfortunately, because of dated translations, some versions of the Bible imply otherwise.
Furthermore, although Jesus must have been familiar with the various Greco-Roman and Jewish beliefs about homosexuality, he never addressed the subject. But he loved and accepted everyone, especially the oppressed and those whom the religious establishment considered unclean. When he made his statement about a man and a woman becoming one flesh in marriage, he was addressing heartless divorce traditions that excessively penalized women. He wasn't saying anything about same-sex marriage, which didn't exist at the time.
An ever-growing number of Christian leaders and laypeople now believe that traditional beliefs about homosexuality are hurting the church, especially its most vulnerable members: young gay people who are convinced that their very essence is sinful. Furthermore, they can no longer support unjust laws that penalize committed gay couples, especially those with children. In fact, a 2011 survey from the Pew Forum on Religion & Public Life found that more than half of mainline Protestants and Catholics now favor legalizing same-sex marriage.
As history has shown, when traditional beliefs are clearly causing hurt instead of blessing, it's worth struggling with the issues involved in order to come out on the other side. If today's traditionalist Christians thoughtfully and prayerfully examine the evidence, it's only a matter of time before they unite with the rest of us to join Washington, Maine, Maryland and Minnesota, and come down on the right side of history once again.
C.S. Pearce is the author of "This We Believe: The Christian Case for Gay Civil Rights," and the director of media relations for Claremont School of Theology and Claremont Lincoln University.