If everyone lost their job or business for being a jerk - and I'm not disputing the fact that he's a jerk, he said some horrible things - there'd be a lot less people employed.
If you work at Foo-Mart, and you make a disparaging, racist comment such that a customer hears it, and that gets back to the manager, you might well face disciplinary action or be fired with cause. You might not, but nobody's going to be surprised if it happens, either.
And if everyone lost their job because someone didn't like something they said, none of us would have a job.
This is a little beyond, "someone didn't like." The guy said that he didn't want a woman close to him even being seen with an African American. Note how many of the players and ticket buyers are African Americans? He said something that the majority of his employees and tens of thousands of paying customers would naturally take as a personal insult.
He owns the team. That means he must keep to a certain level of decorum in his public persona. If he isn't up to it - for example, by being too stupid or arrogant to keep his private life private so he gets caught - then he shouldn't be in that role. Because, really, telling a bi-racial woman that she shouldn't be seen in public with African American men is dumb, and arrogant. He didn't see the possibility that she might just take offense, and think of a way to get back at him for it? That speaks to a lack of savvy that means he's really no longer suitable for ownership.
And no, there is no slippery slope here. This is a very highly-placed individual, being held to the standards required of that position. What happens to him does not logically extend to it happening to the rest of us.