There is a diffrence to having speech and having the right to free speech. There is no fundemental reason that a coorporation should have "rights" as they are regarded and defined in the Constitution. That doesn't mean that they don't have the ability to exercise the same functions, which they obviously do. What it does mean is that law can be constructed to limit their exercise of the same function.
For example, a corporation doesn't have the right to own a handgun.
The Government hasn't made a law restricting a corporation from owning a handgun.
The Corporation may buy and possess a handgun, should it's officers decide to do so.
This is the line of thinking that citizens united over turned.
In the above mentioned example, modified to refelect the personhood of a corporation:
A corporation has the right to own a handgun.
The Government may not restrict a corporation from to own a handgun.
The Corporation may decided to possess any number of handguns, should it decided to do so.
If you replace all mentions of people/citizens with corporation in the Amendments it is pretty scary. I was going to post it here, but after doing the 9th I couldn't go on.