A mid-level comic named Ari Shaffir recorded a special for Comedy Central. In the course of his act he went after a fellow comic for no apparent reason, getting laughs at the expense of her physical appearance and her differently-abledness (she has one arm). She is also, in my experience, a generally decent and kind human being. Skip his Comedy Central special. Check out her Response It is measured, smart and utterly appropriate.
(I've tried to embed her video below. If that doesn't show up, just click the bold text in the paragraph above to reach the video.)