This might be a valid argument were it not for the fact that Facebook itself is not "publishing" the article as such and that (Facebook would argue) it cannot predict or rule how much news feed Facebook users might wish to share. They would argue that it is the Facebook user who is the publisher NOT Facebook and it would be patently impractical to levy a charge against the millions users of Facebook who share news items. If you share a news item with a family member or group, are you publishing that news item in the true sense or merely repeating what you have heard or read?
Supporting the journalistic claim, the Australian Government threatened to bring in a law to mandate payment by social media companies like Facebook for the benefit they get from news items. In retaliation, Facebook temporarily blocked users in Australia from being able to read such news items on their news feeds. In fact, both parties then backed down and a calmer approach is currently being thrashed out.
Whilst there is a degree of logic in the media publishers' argument and undoubtedly people are reading their output without buying a newspaper or article, or subscribing to an internet-based news site, this totally ignores the universality of Facebook and the internet as a conveyor and sharer of information worldwide. As Sir Tim Berners-Lee (the architect of the World Wide Web) himself says "the Australian law could make the internet as we know it “unworkable,” arguing that it “risks breaching a fundamental principle of the web by requiring payment for linking between certain content online.”
Sir Nick Clegg (remember him?) who is now Vice President for Global Affairs for Facebook has today published an excellent article on this subject and indicated the way the affair might pan out. You can read his article here.