The whole point of the first amendment is to protect (amongst other things) freedom of speech for all people. Now the whole point of a corporation is to make a profit and provide a liability shield for its members. In fact, a corporation can be found in violation of its charter if it performs actions that negatively affect its profitability.
Therefore, in certain cases, a corporation may actually be breaking the law if it doesn't spend enough on campaign contributions to sway the outcome of an election away from the good of the people in its own self-interest. This legal necessity arises because of an amendment that is supposed to protect people.
Does this strike you as paradoxical? It does me! But I have a theory about paradoxes. A paradox is, by definition, something that can't exist in the real world, so when they arise out of our models of the world, it means that there is something broken about the model. The Greek philosopher Zeno introduces mathematical paradoxes that wouldn't be solved until the time of Newton, but in the end, even with these famous paradoxes, it turned out that the model used to describe the world was simply inadequate.
In the case here, the obvious flaw is the notion of corporate personhood. A corporation is treated as a legal person, and has been for over a hundred years. I think this idea needs to go, partly because it's antiquated, but on more broad ethical grounds.
Namely, if a corporation is a liability shield, why does it get all the freedoms of a person. Why should it get the same freedom but less responsibility?