When the Constitution was written, free speech meant literally that, your ability to go to a public space and physically talk. No third party was involved as it is with any telecommunication technology. So the resources consumed in that speech were totally your own.
The only way to strictly have that equivalent in the telecommunications realm is for me to own every communication circuit between me and those who I want to communicate with.
So lets say I have 10 wires coming from my house to other houses, and someone I know has 10 other wires connected to a different set of houses, that I'm not directly connected to.
I can rely on my own self and build new wires (expensive) or I can work with this person to forward my communication (probably cheaper but he/she can view/hear my communication).
If I want to communicate with someone else beyond my network, then a third party is carrying my speech, and we're really no longer in realm of free speech. This third party has rights and should be able to refuse to carry my speech for the same rights and reasons as me, unless entered into a contract beforehand.
I think your real question is should corporations be treated as legal persons to the extent that they have the Constitutional right of speech.