I encourage my students to participate in class and think for themselves. I often get questions or remarks about concepts that I teach that stem either from a misunderstanding of an idea, or lack of clarity as to the evidence in support of a theory. I usually find these to be helpful in engaging the class. However, once in a while I get something to which I do not know how to react. This semester, I taught my university's equivalent of Astronomy 101. Toward the end, we discuss the origin and evidence for the big bang theory. I had a bit of a surprise when one of the physics majors in my class became a bit belligerent, asking questions that seemed out of place (e.g., "How can we possibly see light from the Cosmic Microwave Background if it's moving away from us?" - a question that seemed strange since we see things in our everyday lives that are moving away form us). After class, he stayed behind and proclaimed, "The big bang is stupid." I attempted to extract from him what it was about the theory that seemed stupid to him, but never got anything particularly specific. Instead, I received things like, "It just doesn't make any sense," "the universe can't have begun everywhere at once and still expand," and repetitions of, "it's stupid." He then claimed that he wanted to make it his goal as a physicist to prove the big bang theory incorrect. Interestingly, one of my humanities majors had also stayed behind, and was arguing against the physics major's claims of stupidity. I, however, found myself at a loss as to how to react. This person is studying to be a physicist, and I want him to be thinking for himself - however, I found his arguments to be non-arguments, seeming more like excuses for a lack of understanding than keen perceptions of problems with the theory. If the big bang is wrong, I want someone to prove it incorrect, but at the same time I don't want to see a physics major mistaking his own ignorance for holes in the theory itself - and I really don't want the rest of my class to see it that way, either. In the end, I tried to patch up the misunderstandings I could find, but got very little positive response. I was wondering if anyone else had come across a similar situation in any science course, and if so how you handled it. I also would welcome discussion on this type of situation in general.