Please read the Citizens United majority opinion, and listen to both oral arguments; I think you will find that CU had a much better argument than you might think. Although you may dislike the consequences of the case, the government's argument was horrifically bad. In short, the government argued that the FEC could ban books and magazines, if they felt the publisher should not be granted a "media exemption", and that this ban would comply with the first amendment ("Congress shall make no law... abridging the freedom of speech").
That might be so, but the court still had the option of narrowly allowing the items you point out without opening the floodgates. They went for floodgates.
In some circumstances, courts can narrowly decide cases, but where laws violate constitutional provisions by over-breadth, the Supreme Court strikes down the laws in their entirety.
So your issue wasn't with potential FEC overreach as you argued above, your issue is that you agree with the Citizen's United decision in whole, and are all about the floodgates being opened. We'll just have to disagree on that.
I think the two issues are inseparable (for better or for worse). The government required a great deal of power (in violation of the first amendment) to regulate and prevent express advocacy. The court had to strike down the laws as unconstitutional, to avoid allowing the government to put "prior restraints" on the freedom of speech. The only way to avoid this would have been to reach a narrower decision, based on an entirely different basis, but this could not be done once the 'prior restraint' issue had been raised.
I suppose that I simply do not understand why the ruling was so controversial; it does not make sense to me that General Motors could be restrained from publishing certain things, and that General Electric (which owned NBC at the time of CU v. FEC) would be allowed to publish whatever it wanted, because of its media exemption (as was the government's argument).
