I recently went through financial difficulties that involved problems paying 5 different credit cards. Bank of America was by far the most helpful company, actually recommending that I enter into debt management to allow me to pay off my cards at a markedly lower APR without taking a huge hit to my credit.

How exactly are they evil? They borrow your money at a certain rate, and loan it to other people at a higher rate?

Without getting into the evil/not evil argument: This is not quite correct. A bank can lend more money than they have/borrow. The bank must only maintain a specific ratio of equity and loans. For more details see Basel I, Basel II and the upcoming Basel III, which (should) regulate the loans of banks.