I don't think that could help, because you have a person with many followers and in their mind they think they are doing a good thing to spread "the message" so

I don't think that could help, because you have a person with many followers and in their mind they think they are doing a good thing to spread "the message" so they would push their message to as many people as possible. I was thinking you could have say a way to tag your posts or shares so your professional posts and personal posts could be separated but the "activist" would ignore the tags so they push their message to everyone. So as other suggested you would need a filter on client side to get around people that attempt to push some to everyone.