Professor Stephen Bainbridge is a nationally recognized expert and prolific scholar on corporate law topics. Judge Richard Posner is a prolific member of the U.S. Court of Appeals for the Seventh Circuit who writes many books on many topics. Professor Bainbridge writes here about his disagreement with Judge Posner’s recent writings about Catholicism, and in particular how the judge has his facts wrong, for example, as follows: "Neither as a legal, theological, nor practical matter is the Roman Catholic church viewed as a single corporation." Read more at the above link for more detailed analysis regarding the "clash of the titans".
Postscript: Joseph Lawler adds his viewpoint here.