I've never seen the film, so I had no idea what they were talking about, from the short documentary on filming locations:
Apparently, walking and filming the Exorcist steps is a popular past time: "Drunk white guy climbing the steps from the movie."
"Exorcist" author, William Peter Blatty, is a Georgetown alumnus and wants Vatican to excommunicate Georgetown from Will Thomas May 14, 2014 Fox report "Is Georgetown University not Catholic enough? Vatican responds to petition from 'Exorcist' author"
"William Peter Blatty, wrote the Vatican voicing his concerns that the Georgetown campus has become too liberal, calling both students and faculty out for not being aligned enough to the Catholic faith.
Now, the Vatican has responded by saying his complaints are well-founded."
Why go to a Catholic Jesuit university if you want to be an atheist?
“One of the things I like about Georgetown is religion is what you want it to be,” said senior Alex Kyrillos. “So if you’re someone who wants that to be a huge part of your life, the resources are there for you. But if it's not something you want to be a huge part of your college experience, you also have the option.”
Seems Blatty was working with Cardinal Newman Society to petition Vatican, from article Michelle Boorstein May 13, 2014 "Washington Post" article "Vatican responds to Georgetown petition by ‘Exorcist’ author William Peter Blatty"
"The effort was brought by Blatty and a group connected with the Cardinal Newman Society. The campaign represents the frustration of some conservative Catholics who want to see Catholic institutions more orthodox and uniform. They rally around Ex Corde Ecclesiae, a 1990 document by Pope John Paul II that gives instructions to colleges and universities about how to keep their Catholic identities."