If there is no difference in the moral beliefs of an instructor at a Catholic college, why should I pay $30,000 a year to send my daughter to University of Detroit Mercy as opposed to $9,000 at Oakland University?
We aren't talking about algebra instructors at the local community college. We're talking about tenured and visiting professors at some of the most prestigious academic institutions in the country. They aren't hiring people who are dropping off apps at the HR office. These colleges are recruiting the best subject-matter experts that they can get their hands on, people who are published and well-respected in their academic fields of study.
I wouldn't be surprised at all to learn that the professors in the physics departments at Boston College, Notre Dame and Georgetown were ALL committed atheists. Why? Because the great majority of the world's most accomplished physicists are at best agnostic. If you want your students to be exposed to the greatest minds available, you don't limit your faculty to "true believers" - not if you are really committed to academic excellence. They are not running madrasa to indoctrinate kids in a religion, they're running a great university.