Translation:This is a Catholic church, that is a Protestant church.
You would be surprised how many young Americans would make the same distinction. I was once teaching a medieval cultural history course and was asked by a student about two thirds of the way through the course whether we would ever read any Christian texts. We had read not only canon law, scholastic quaestiones, and saints' lives, but even some selections from the New Testament.
I've spoken to evangelical Christians in Australia with the same opinion, but they are coming from a place of cynicism rather than ignorance, believing that Catholicism is not true Christianity.
I disagree and in the context of this sentence, agree that "that is a protestant church" should be the preferred translation, but "...christian church" should continue to be accepted.