Unfair discrimination?

This is from an article in The Scotsman: "Atheist teacher at Catholic school was 'second-class citizen'." One wonders why Mr. MacNab finds it so outrageous that a Catholic school should prefer a Catholic to an atheist for the position of principal teacher of pastoral care. Would he think it amiss that an atheists' society would pass over a professing Catholic in filling one of its own leadership posts?