The legislation in question, the Bipartisan Campaign Reform Act of 2002, was not concerned with "granting free speech to some corporations and not to others", which is the way you are trying to frame it. It was concerned generally with campaign finance reform, and specifically with putting limits on how much and what types of contributions corporations are allowed to make to political campaigns and what must be disclosed when they do so. The part of the legislation that made it vulnerable to the Supreme Court decision was its effort to regulate issue advocacy ads, or so-called "soft money" influences on political campaigns. The legislation had some issues, but it was more or less reasonable: it defined "electioneering communications" as broadcast ads that name a federal candidate within 30 days of a primary or caucus or 60 days of a general election, and it prohibited corporations and unions from paying for such ads. That's really it. Fairly narrow in scope, not a blanket ban on free speech or talking about politics or any such thing.
Regulating corporate influence on our political campaigns has a long history. It is not a new idea invented by liberals to suppress conservatives. In addition to the BCRA, there is the Federal Election Campaign Act of 1971, which has been amended several times and regulates contributions to political campaigns, parties, and PACs. It also implements disclosure rules. Before that there were several smaller bills, including the Federal Corrupt Practices Act of 1910. What I'm trying to say is, the influence of money on the political system has been recognized as a problem for more than 100 years and there have been many efforts by both major parties to regulate it.
Before the Citizens United decision, campaign finance reform was not considered an issue of free speech, and it did not specifically favor one corporation over another. It targeted all corporations. It prevented a specific narrow type of political ad from being distributed in broadcast media channels during specific time frames leading up to major federal elections. It being 2002, the Internet was not a medium of much concern (so anything on the web would have been exempted, including political blogs). The Act in effect only targeted TV and radio. The FEC has a nice summary of the bill posted.
An electioneering communication is any broadcast, cable or satellite communication that fulfills each of the following conditions:
The communication refers to a clearly identified candidate for federal office;
The communication is publicly distributed shortly before an election for the office that candidate is seeking; and
The communication is targeted to the relevant electorate (U.S. House and Senate candidates only).
The regulations at 11 CFR 100.29(c)(1) through (5) exempt certain communications from the definition of "electioneering communication":
A communication that is disseminated through a means other than a broadcast station, radio station, cable television system or satellite system. For example, neither printed media-including newspapers, magazines, bumper stickers, yard signs and billboards-nor communications over the internet, e-mail or the telephone are included;
The Supreme Court decided to overturn all of this, not just with Citizens United, but several other similar decisions as well. The advocates say "hey, free speech is free speech", and the detractors say "hey, this is opening the flood gates to unlimited corporate spending on political campaigns". However you choose to see it, it is not a simple problem with an easy solution.
So to answer your question,
Just in general, if you give the government the power to decide which corporation is and is not in some special category when it comes to free speech, you've ended free speech. Surely you can see that?
Yes, I can see that, but that is not what the BCRA or the Citizens United decision are about. Can you see that?