Does liberalism have any room left for Christians and other believers? The question has been posed countless times, and each time liberals answer more decisively than the previous: No.

On Thursday Britain’s Liberal Democrats delivered that message to their leader, Tim Farron, forcing him to resign over his mildly conservative views on homosexuality and abortion. The Lib Dems supposedly carry the torch of 19th-century classical liberalism, though more recently it’s been difficult to distinguish them from any progressive party,...