I've recently finished grading one of the take-home tests I give for my Intro courses; it's a test on the history of philosophy, and is a rather difficult two-part test, so I throw in a lighter question or two. One of them is simply to name something they learned from the course that is not on the test. As you might expect, there's a wide variety of answers, but one answer I've come to expect, which is virtually always mentioned by one or two students, is that they were surprised to discover that there were any Christian philosophers. That is to say, any Christian philosophers ever. Sometimes I get a more generalized form, expressing surprise at the existence of religious philosophers of any sort.
They learn that such people have existed, of course, because I always have a medieval philosophy segment to the course, and all the philosophers there are Christian, Jewish, or Muslim and, because it is convenient for giving some order to the period, explicitly labeled as such. I think of this as being to some extent a vindication of teaching Introduction to Philosophy with a historical approach, despite the difficulties it introduces: had I not taught this course several times, and if I taught it by problem-units (free will, skepticism, etc.) rather than by historical sweep, it would never have occurred to me even to raise the point explicitly -- it's the sort of thing I ordinarily take completely for granted. And, whatever one may think about the interest of that point in general, this is a matter that is undeniably a point of interest to many students: I mean, there are students whose minds are seriously just blown by it, and all their preconceptions of philosophy smashed into bits by it.
One wonders what the background causes are that lead so many students to disassociate the concepts of philosophy and religion, but it's not an uncommon thing. The number of people who, on discovering (usually through different channels) that I'm both Christian and teach philosophy, have actually been taken aback, and puzzled about how that could possibly work, is extraordinary. It can't be any well-defined conception of philosophy. I find that most people, that is, most ordinary people going about business that has nothing to do with academia and have never taken a philosophy class before, have difficulty keeping philosophy and psychology straight. And (for instance) it's not difficult to find people whose conception of philosophy is that it is a sort of koan meditation; in their mind philosophy works by coming up with questions that have no possible answer -- not many possible answers that can't be narrowed down but no possible answers at all. (This is, incidentally, worth keeping in mind when one teaches philosophy, because such students can go through philosophy courses without ever being disabused of it, since they have no problem with saying that such questions can look like they have answers, or that people can think they are giving answers to them. But a lot that is puzzling about the way students respond to, say, trolley problems or skeptical scenarios suddenly makes sense if you assume that some of the students are assuming from the beginning that posing a trolley problem or skeptical scenario is like asking about the sound of one hand clapping. To them it's a category mistake to think that one can really get any farther than merely posing it.) But it is very, very common. Perhaps the heavy emphasis on skepticism that has been such a common staple of the modern undergraduate philosophy class is a contributing factor; but, again, we are talking about people who have never had an undergraduate philosophy class before, and whose acquaintance with the very term consists entirely of pop culture references and whatever might come up in ordinary conversation.