"Keep your friends close and your enemies closer" might come into play here. If the President ran Holder off, what could Holder do or say to taint the President's image?
Holder has been a disaster and I don't know how Obama has not told him to resign yet.
I'm not for sure how Holder's reputation is still holding water. I thought for sure that "fast and furious" was a big deal but its never talked about anymore. (There's no way that he didn't know what was going on. It is his job to know what was going on.)