Why Rawls? and 138B

So I read about half of the actual Rawls text (still going to read the rest before class), and I don't understand why we're reading it for this class.  We're studying communication ethics.  I understand the readings on that.  I understand the readings on ethics in general.  Rawls specifically says that he's restricting attention to political justice, and not trying to write about ethics ("morality") in general.  So:  Why Rawls?

Here's Colour Record No. 138, Side B: