Tonight I found an important paper by William Cunningham, entitled, “The Principles of the Reformation Not the Cause of Sects and Heresies,” in James Wylie’s Tercentenary of the Scottish Reformation, pp. 108-123. The charge that Protestantism produces thousands of schisms and sects is frequently bandied about by the likes of Scott Hahn.
You can find Wylie’s book here.
I appeal to you, brothers, to watch out for those who cause divisions and create obstacles contrary to the doctrine that you have been taught; avoid them. For such persons do not serve our Lord Christ, but their own appetites, and by smooth talk and flattery they deceive the hearts of the naïve. (Romans 16:17-18)