The point you are missing: this business considers itself to be a content creator and value adder, and they do that because Facebook has previously encouraged that. Now Facebook are saying that they don't care how compelling your content is, if you are commercial in any way, you have to pay. That's not how a social network is meant to work.
Who exactly defines "how a social network is meant to work?" Seeing as Facebook is one of the two most defining social networks of the social network era I think they at least have a say.
Who exactly defines "how a social network is meant to work?"
The users do. Facebook will see declining participation if they keep taking user-hostile actions like this. People need to feel they are in charge of their feed (at least mostly in charge), but if they no longer control who sees their content, or which content they see, and hence become unhappy using the service or use it less, that's going to be a big problem for FB.
