Pretending like they are a vehicle for collective speech merely amplifies the speech of the owners at the (potential) expense of the employees. Perpetuating the facade is sadly both another symptom and a furtherance of the corrupting influence of money in our politics.
An argument could be made to have different rules for benefit corporations and non-profit corporations as opposed to traditional for-profit corporations.
It’s simple enough to draw the line at registered organizations. These entities after all are afforded distinct legal privileges.
The bottom line is that any restriction or redefinition of civil rights is fraught with negative unintended consequences. It should be an option chosen with extreme care.