Liberal Protestantism is a victim of its own success, according to the late Robert Bellah, a sociologist who specialized in religion. In a process that he calls “Protestantization,” liberal Protestant values have influenced secular humanism to the point that they are indistinguishable.
This apparent victory is also a defeat, suggested Bellah. He argued that such widespread success simultaneously diminishes liberal Protestantism’s distinctiveness, at the same time that it dwindles the congregation size of churches. He observed,
There is more than a little evidence that most Americans, for example, would assent to unmarked liberal Protestant beliefs more often than to unmarked orthodox alternatives, and that this would be true not only for most mainline Protestants but also for most Catholics and even most Evangelicals.