It seems to me that if the “freedom of speech” clause of the First Amendment to the Constitution means anything, it means that people should be free to engage in criticism of politicians and policies without being controlled (beyond libel laws) by the government or political parties. Paying for political advertisements with your own money is certainly a means of this type of speech.
No sensible person believed that the McCain-Feingold campaign finance reform bill would get rid of negativity from political advertising, or the ability of moneyed interests to have a large influence on politics and politicians.
That Bush and McCain now claim that they did is pathetic!
Jacob Sullum’s summary is a good one.