Among Cardinal Robert McElroy’s seemingly multiple objections to Catholic teaching is its sexual morality. For McElroy, besides being unwelcoming and off-putting, Catholic sexual ethics distorts Christian moral life as well as makes assumptions that he rejects, by misusing in this context the old category parvitas materiae (“lack of serious matter”). In plain English, he rejects the notion that sins against the Sixth Commandment by their nature are mortal sins…