You don't seem to know much about universities. For many majors, there absolutely are required courses that absolutely everyone in that major will pass through, and for a span of many years there is only one professor teaching the course.  He wasn't saying every Columbia student passed through his course. You'd be right if he had. He said every political science major.  As for addresses, same as having Columbia administration backing him up: a plant. If he'd really been there, there would be more than that.