Question

what is the purpose of representing disturbing  things in art?

Answer 1

Keep in mind that art is not only an important means of communication but it is also extravagant way of drawing attention to something out of the ordinary, be that good, ugly, revolting or 'disturbing' as you say. Also, artists are not silent or peaceful souls on the Earth: they are inquisitive, introspective minds that possess a rebelling and extremely passionate heart. Though their work is silent, they can be very persuading along the history.