Already said above but with slightly different wording:

The sentient individuals who act in multiple ways through and with a coporation have inalienable rights to free speech. Most of them will have no realistic way to resist the power of the mob which is the larger bulk of the people (with varying degress of authority and discretion) in this legally manufactured "entity" that exists only under the laws created to allow the concerted efforts of all these people to function in certain multple ways. People delegate much of their authority to the corporate "leaders," i.e. directors who might re-delegate to executives, but if you do not constrain the corporate "rights," you will be impinging upon the free speech rights of individuals. Can an individual delegate free speech rights to others, even in advance of knowing what the words will be? Would an individual ever choose to do so? Some would, some wouldn't.

Constituional rights of individuals require constraints on the "rights" of a group.