This semester I started attending a seminar on (I'm translating from German hear
Let me make a remark in support of your long-winded professor, and I am afraid that sort of pedagogy does rather go with the discipline.
I think your professor is right, and perhaps he felt he needed to make the point at some length, as often happens in such cases. Art does have a role in society, but then so do many things, and unless you know what art is, how can you distinguish between its role and that of other cultural forms? Many things are used to communicate also, and not all of them are art, so it is worth spending some time deciding what art actually is first.