You got me. They are a split-off of the the Southern Baptists. They didn't like some of the stands the Southern Baptist Convention was taking. They are liberals, with the liberal agenda conflicting with the conservative Baptist doctrine. So when you hear about them, you can just figure "Here's the liberal democrat Baptists that founded their own denomination so they could be more comfortable."
More power to 'em, I say. At least they are gone and not tearing up our traditional S. Baptist churches. A local church here in Tulsa is in such a tumult over just this kind of thing. The pastor is liberal, the flock is conservative.