The problem here is that SEVEN carriers carry almost all traffic in the US. Most smaller cities are only served by four or less.
If you live in Portland, you have three choices in peering. All of them are large corporations. If those three decide to block your traffic, you have no recourse other than to leave the state, or invest $100 billion in creating a new backbone, and then arrange peering agreements with all of these companies AND provide direct connectivity to the content you want published.
The problem isn't necessarily Fox News, because they have a substantial demographic, but rather, for smaller groups. Sure, it is nice to think about blocking the KKK or something similar, but what about other somewhat fringe groups like radical libertarians. The first amendment says the government cannot prevent their speech, but what if three major backbone companies decide to restrict it? They are effectively wiped away. There is no "soap box" if you are compelled to stay inside your "virtual" house by corporate owners.
The government stepped in (rightly) when the 19th centry mega-corporations began to dictate local laws with their wholly-owned corporate shantytowns, where employees were required to live.
But in a digital era, when more jobs are going online and most communication is online, a corporation restricting speech is just as dangerous as the government doing it, because the corporation is the de-facto government of the internet, by the nature of their control over its traffic...
Unless there is some rule that says otherwise.
I regard net neutrality akin to the first amendment or the anit-monopoly laws in "meat space". They are simply that important.