Hard to tell whether that's really a "slur" on folk music or a slur on the way certain programs are conducted. The academic study of folklore & folkmatter (obviously including music) has been pretty well respected for several hundred years, from Percy through Child, etc. So it's doubtful that anyone aiming at credibility would badmouth that. OTOH, if some school's offering Master's Degrees in the Kingston Trio, then Clinton's comment might well be right on the money, though certainly some graduates would also have to master "You want fries with that?"