Facebook is entertainment, not news.
Having an expectation of accuracy is to mis-understand why people are there in the first place.
The furor about "news" on Facebook is really all about people who don't read the newspaper, don't watch the news on TV, and aren't reached by normal media in the first place. That they are now getting their "news" in the form of entertainment with no real obligation to accuracy bothers those who do read newspapers, watch TV and listen to radio news programs, and live in academic worlds where these kinds of things are the basis of their "work".
Let's not forget that this is also a fight between traditional Media and Social Networking Media. As expected, the more serious news outlets are playing the story big, because their "bread-and-butter" requires that they be taken more seriously than made up drivel. Where people get their media is important to them, because it is "them" that will lose if they fail to at least make the issue in the forefront. There are battles at other quarters they are also fighting, where serious journalism can be dismissed with an offhand remark. They are in a fighting mood, basically.
But realize that these poorly-informed citizens have always existed. They voted at the turn of the 20th century just as often as they vote at the turn of the 21st, and with about the same accuracy in information. It just annoys some that with literacy that still exists.
Certainly there is no need to increase the amount of poor history and news reporting but personally I think the panic is overblown. Facebook is just what it is.
I also think that people's ability to self-censor what they see and read on Social Media is under-estimated. Just because something is posted on FB doesn't necessarily mean that everyone who reads it believes it.