What's a little jab at the legitimacy of your worldview between friends?

I was put on the spot at a party in order to defend modern art's legitimacy AGAIN. Um, do people not know it's impolite to follow up the question, "what do you do," with the demand to prove that a) art--and by association my PROFESSION--is not a hoax, b) the subject of my degree is not something their child could do, c) that artwork is, in fact, worth its monetary value and not some grand scheme to line the pockets of that massive army of filthy rich artists we all know is taking over the world. "But why can't I understaaaaaaand it?" they always want to know. Somehow the reply, "Because you're not very smart," is not on the table. The question sets me up for failure: what am I going to do, explain every single meaning of every twentieth century art movement to some jerk at a party?