Unfollow by campaign?

Thanks for that question!  There isn't a way to unfollow people based upon campaign.  Most users unfollow people based upon how long it's been since they followed them and whether or not that person has followed them back.  That workflow is why we made the Unfollow People a separate entity and allow users to filter based upon when they followed people and other filter options.  

In summary, what you are attempting to do is possible just not by specific campaigns.  Let me know if you have any questions!