In Defense of Citizens United
In a nutshell, much of what has traditionally been protected political speech uses the corporate form. I'm open to suggestions, but I can't see how you can draw a reasonable boundary between protecting the New York Times Company spending millions of dollars to distribute an election editorial and not protecting Koch Industries spending millions of dollars to run ads during an election.
I usually hear one of two responses for how you would draw such a distinction, neither persuasive to me.
The first is to argue that the First Amendment should protect the right of individual persons (such as journalists) but not cover the corporate entity (such as the New York Times Company). The problem here is that this would still enable overly broad restraints on what many would consider legitimate speech. Journalists may be free to write what they want, but they wouldn't be able to receive a corporate salary. Or use the corporate printing press. Or post on a website owned by a corporation. Or really do anything more than standing on a street corner and handing out flyers.
The second is to draw a line between different types of corporations -- e.g. between media and non-media corporations. This is the approach taken by the dissent in Citizens United, but it's one I'm uncomfortable with because of the difficulty in drawing coherent boundaries here. Take the media / non-media distinction for example. What's a "media corporation"? Is the New York Times a media corporation? What about Google, which hosts Blogger? What if a non-media corporation bought a media corporation? First Amendment law favors bright lines because fuzzy boundaries have a chilling effect on legitimate speech. And the lines involved with okaying some corporations but not others aren't so clear in practice.
While I'd like to think there's a line to be drawn here, but I suspect there isn't. The fundamental complaint raised by campaign finance reform activists isn't about corporations per se, but about how the accumulation of capital affects the political process. Yet the political process is built around mass communication. And it turns out that communicating to hundreds of millions of Americans is expensive. It requires the accumulation of capital, whether it's paying for TV broadcasting, print newspaper, or laying the fiber optic cable for an Internet connection. So long as that's true, it'll be difficult to take the money out of politics without taking free speech out as well.