I'm reading Garry Wills' Head and Heart, on "American Christianities," a good read but a slanted and provocative polemic. It's slanted against traditional conservative orthodox Christianity and in favor of what Wills calls "Enlightened religion," which is any theologically or socially liberal religion.
Consider his treatment of the Quakers -- one of the first Christian sects to oppose the practice -- and slavery.
The Quakers made possible all later forms of abolition by proving that one can be a sincere Christian and yet defy the scriptural endorsement of slavery. If reason says slavery is wrong, then it is wrong no matter what the Bible says. They also proved that Enlightened religion is indeed a religion. They are stellar exemplars of both religion and Enlightenment. p 152.