you still have to protect the Constitutional rights of the people who make up the corporation.I'm now starting ... dimly ... to understand what your issue is. Maybe.
To me, the humans do not "make up" the corporation, in the sense of being part of it. The corporation is a legal construct that protects them, the humans, from certain problems. It's like a building: it is not "made up" of the humans it protects, and they can move in and out of it at will.
The building -- the corporation -- has no human or civil rights, because it is not a human being. The fact that US law currently gives corporations partial human status is not something of which I approve: I consider "corporate personhood" a sociopathic abomination.
Anyway, to me the analogy is this: "corporate political speech" is like the building owner putting a huge sound system on the roof to blare out his political beliefs night and day. It becomes very difficult for actual human beings to have conversations down on the ground, because the building has given the owner such power over the whole social space.
But it seems to me that Sebastian (and 5 members of SCOTUS) are saying, "the building has rights, too! how dare you restrict the building's speech!" Or maybe it's that the owner has rights, and those rights include the right to be protected by the building (from, say, the squashy tomatoes of civil discourse) while using the building's power to amplify his voice.
I think maybe I've gotten tangled in my own metaphor.
In any event, I don't see why the idea that powerful people should get *both* extra protection (via limited liability) *and* extra volume for their speech doesn't repell you. But maybe my theory about the essence of conservatism is right: political conservatives *like* and desire that those who are at the top of the power hierarchy should stay there. Maybe you find it reassuring that very wealthy people should have their way smoothed to drown out any other voices.