Social media is definitely harming society. People can now quantify "social approval" through a system of points. Humans seek validation, and in order to get validation they say things they think people will like that will reward them with these "points". This leads to an echo-chamber of mass conformity whereby people may not necessarily believe what they are saying, but they will repeat it for all the world to see so that they can be validated by their peers. In time, they will come to "half-believe" the absurd things they think they must say. Unfortunately, not only is this disastrous for the human race, it's also gamed by the businesses and organizations that own these systems. Organizations now reduce the visibility of opinions that they don't like in order to reduce the amount of social validation points a person will get, or increase visibility to reward that person. On the whole, people will be guided through a Skinner-box designed to condition them into accepting a certain political and philosophical ideology that is arbitrated by whatever happens to be the ruling class.
I believe that this is far worse than anything humanity has yet encountered. When kings(as an example) wished to control speech and thought, they had no method of not only being able to entirely silence a person, but also make them believe that every single one of his peers held some belief by hiding or silencing those that shared his belief. Today, that ruling class can make a person whose belief is shared by the vast majority feel as though he is some wacky outsider with insanely divergent beliefs, thereby making him fear to speak or act. Through the media and social media the ruling class can now arbitrate truth can control peer review respectively.