I didn't see the big deal at first but Colin Cowherd spelled it out nicely. It's got nothing to do with politics. Fact is most of the owners are Republican and probably share his opinion on a lot of things. The NFL wants two things among owners - a uniform voice and QUIET.
Al Davis, Jerry Jones are high profile owners but you never hear them bad mouthing the league or teh game. The NFL doesn't want a Mark Cuban-like owner who runs his mouth about players, refs and anything else he can think of. Cuban doesn't fear the repercussions of what he says. He willingly pays whatever fines he gets. Rush would do the same because he can afford to. Even worse - he has a national radio platform to say whatever he wants, like his Donovan McNabb/the NFL wants black QB's comment, whenever he wants.
People think this is about Rush interfering with the team, not signing black players and other nonsense like that. He'll have no say in how the team is run. I bet there's 53 guys in Oakland right now that would take Rush over Al Davis any day of the week. The NFL just doesn't want to get into trying to fine him into being quiet and having to fine players who respond to whatever he says and so on and so on. Owners want it nice and quiet in the owner's box and Rush will be anything but that.
Keep in mind Mark Cuban caught all manner of flack when he wanted to buy the Chicago Cubs. He was willing to pay $300-400 million more than the next guy. Cuban did not get the team because MLB feared he would never STFU...and he's a Democrat. You're short sighted if you think this is politics.