Well there's a couple reasons Brian......all of which you're perfectly aware of. Let's see.......
1) First and foremost, the NFL is comprised of 70% black players......the days of playing for a "Massa" like Limbaugh just doesn't appeal to them. They already don't like the league for penalizing them if they so much as raise their voices in triumph after a touchdown. This one's pretty simple.
2) To kind of go along with reason 1, he's a bigot/racist....no real debate there.
3) for the above reasons, he's bad for the NFL "brand". I'm really surprised at his reaction to this because he's made a career out of complaining about affirmative action on the basis that a business owner should have the leeway to hire/fire whoever he chooses even if it's based on a superficial reason such as skin color. So in this case, the NFL has chosen not to do business with him because it could potentially affect their ad revenue.....especially "WHEN", not if, when he opens his fat trap and makes the comments he's so known for and quite frankly get's off on. The NFL is simply afraid he may at some point affect their sponsors. Valid concern. Just like NFL teams for the most part wanted nothing to do with Vick.......bad for the image.
And no, it would not increase NASCAR's ratings if Olbermann bought a team. Nobody would care. Nascar would still lick ass.