Apparently his now ex-girlfriend is involved in a legal dispute with Mr. Sterling, which may or may not taint the authenticity of the recording, depending on your point of view. But now apparently this is a national story which requires everyone's personal take on it. So I'll offer mine.
If the accusations are true, it's pretty clear that Sterling is a racist asshole. What should the NBA do about it? I don't know. This isn't a free speech issue; I don't think anyone is advocating that Donald Sterling be put in jail for what he said. If and when the NBA takes disciplinary action against him, it won't be in violation of his rights. He voluntarily gave some of those up when he chose to buy a team that belonged to a sports league. While he may be "in charge" of the Clippers, there are things he can and can't do as a member of the National Basketball Association. Owners, coaches, and general managers get fined for all sorts of things that are not illegal (like criticizing a referee, or accusing league officials of conspiracy) and it's ok.
So I guess I'm ok with the NBA fining him. I'm ok if they want to black list the Clippers from prime time games or other perks while he is owner. I don't think I support the league forcing him to sell though. The backlash he's facing so far seems to be a suitable replacement for such a dire action as a forced sale. Nutcase owners tend to not do so well. I would know because one of my favorite teams has had one for a while, and the team stunk until fairly recently. Failure tends to be its own punishment.
And for the record, the NBA is not a typical business. There seems to be some people concerned that the backlash against Sterling (and the former Mozilla CEO from two weeks ago) might mean that other office environments might crack down on unpopular political views among its employees. The analogy is nonsense though. My employer doesn't broadcast my workday live on TV or radio. My employer doesn't rely on a TV deal or advertisement revenue to make money. The NBA does. And if the NBA runs afoul of a great number of its viewers, its business model is threatened. So anyone criticizing the NBA's response and concern really has no idea about the nature of public relations.
So there you go, Donald Sterling is no hero. He's not a free speech martyr. He's just a racist asshole who should probably get what's coming to him.