> emails of people who have clicked on an ad, or entered their email saying they support A, B, or C and give them permission to post a comment on their behalf

Even supposing they did it this way, and people gave their informed consent (fat chance, but for the sake of the hypothetical), that's still fraud. Unless every single comment had a "written and submitted on behalf of X by firm Y" disclaimer, it's still misrepresenting the comments as coming directly from individuals.

Regardless of what fine print unwary consumers agreed to, the agencies being deceived didn't agree to any of it.