He then says there is no way such an amendment could pass, which is true. Lots of liberals think corporations should have no Free Speech rights, but I don't. I just don't think you could create a coherent legal structure that got the outcome Brendan is looking for. (I'm not picking on Brendan, but his post is just a handy starting point for me to make this argument.)
First, notice that the call is for is no free speech rights for for-profit corporations, except the press. Nice phrase, "the press". But what that phrase refers to are some huge, for-profit corporations. We really mean things like Rupert Murdoch's News Corporation, Viacom and Time Warner. Why is it better that those behemoths have the legal right to free speech, but other large corporations motivated by exactly the same profit-seeking do not?
Then there is the line-drawing problem with "the press". What kinds of corporations do we include and which don't we? A lot of the big media companies mingle news and entertainment (and often you can't really tell the difference). Is Comcast "the press" now that it's taking a controlling stake in NBC Universal? Hell, is NBC even "the press", since the news division is such a small part of NBC?
The Public Citizen petition that Brendan links to is careful to call for no free speech rights for for-profit corporations. That's smart, because Public Citizen itself is a corporation, but a non-profit one. There are lots of non-profit corporations that advocate for political causes across the spectrum, from the American Civil Liberties Union to the National Rifle Association. No one, including liberals, seems to think it's a problem that those entities have the right to free speech. But where in the Constitution does it say that non-profit corporations are people? Nowhere.
To top it off, for-profit corporations often set up and control non-profits to carry out various purposes. If you amend the constitution to ban for-profit corporations from having free-speech rights but retain it for non-profits, companies will just create nonprofit subsidiaries for the purpose of speaking.
While I think Citizens United is wrongly decided, some of the reasoning in the majority opinion is sound. The Free Speech clause doesn't just protect the right of speakers to speak, it protects the right of listeners to listen, and be informed or persuaded. That's the underpinning of what we shorthand as the marketplace of ideas. If there was a right to speak but no corresponding right to listen, the protection would be meaningless. If you want to protect the right to listen, then you should be inclined to think that more speech is better than less speech, absent a really compelling reason it's not.
One objection to corporate free speech is that corporations are motivated by money. That objection proves a little too much. Lots of people are motivated by money and their speech reflects that motivation. In fact, that's a good thing, not a bad thing. Free speech means that the people who have a stake in some matter - whether it's financial or otherwise - can tell other people about it and enable society as a whole to respond in an informed way. That your livelihood is being affected is a great reason for you to have the right to speak, not a reason to curtail that right.
Just because the text of the constitution doesn't grant rights to corporations is not a conclusive argument that those rights shouldn't be granted. Rather than being literalists and originalists, liberals usually believe that the definition of rights under the constitution should change to protect the principles embodied in the constitution as social realities change. As an example, abortion is not mentioned in the constitution, but we believe that there is a constitutional right for women to control their reproduction based on the principles of autonomy and privacy in the Bill of Rights. For better or worse, corporations are an integral part of American society. The objection is that they are too powerful already, which I agree with and which is part of the reason why I think their direct political activity should be and can be limited within the bounds of the constitution. But saying that corporations should have no free speech rights at all would mean that a huge chunk of financial resources will be put behind a firewall where it can't participate in debate in any way. Some people would say that's good; that to corral the power of large companies, their wealth should be walled off from use in public debate. But not all corporations are large corporations. Small and medium-sized companies are a large part of the economy. The owners and operators of those entities often have all of their personal fortunes tied up in the businesses. A complete ban on corporate speech would mean those people would be unable to use their resources to speak out on things that would affect them directly, even though it's not these kinds of corporations that liberals fear have too much power in society.
What I think is a perfectly valid criticism is that in large corporations, the officers and directors rather than the shareholders are effectively in control of the entity's resources. That creates a set of incentives for those officers and directors to use other people's money to speak on matters in ways that the owners might not approve or even be interested in. And large corporations do concentrate wealth into the hands of a very small number of people to the point that there is a real risk of undue influence on government. As corporations get bigger, they begin to look less like voluntary associations of people which we can reasonably say speak for all their members and more like Frankenstein's monster - a powerful, artificial construct that has none of the motivations or limitations that a natural person has.
The issue is corporate political speech, not corporate speech generally. I think that as a society we have a compelling interest in preventing large accumulations of wealth - in the corporate form or otherwise - from distorting our political system even further than it has been, completely replacing the principle of one person, one vote with one dollar, one vote. If corporations have a free speech right to create political ads, then why shouldn't they also get to make donations directly to candidates and parties? For that matter, if money is speech, and the Court has decided that more money is good for politics, then what should prevent individuals and corporations from making unlimited campaign contributions? From there, you're just one step away from selling individual elected positions to the highest bidder. I think there are really good reasons to keep our political process as close as we can to one in which individual voters really are in control of who gets elected, and to me that justifies both individual contribution limits and a complete ban on corporate political spending. But depriving corporations of all free speech rights in order to accomplish that goal would be almost as bad as what the Supreme Court did today.