Mutiny in the church...
(Tim, w/thanks to Steve M.) Read this post by Carl Trueman. It's almost excellent.
Almost because, sadly, the salient point to make about it is that there are no specifics mentioned, no men and their errors exposed. Sadly, that neglect says more than the good words Trueman has written.
To warn against theological and ecclesiastical and confessional and Biblical rebellion without warning against any particular man is to gnaw with gums instead of chewing with teeth. Until you name names, it's only one more hypothetical construct.
It wouldn't surprise me if reformation 21 had a policy against questioning or warning against any particular man's faith or practice--particularly if that man sells lots of books and is cited more than anyone else by Reformed pastors, today.