The “spiral of silence” is a well-researched phenomenon in which people suppress unpopular opinions to fit in and avoid social isolation. It has been looked at in the context of social media and the echo-chamber effect, in which we tailor our opinions to fit the online activity of our Facebook and Twitter friends.
Source: Mass surveillance silences minority opinions, according to study – The Washington Post
Rather than increasing perspectives, social media naturally enforces a conformity in ideas, in order that people avoid feeling like outcasts. Consider this in terms of social media propaganda: if your news feed is filled with propaganda posters expressing group beliefs (even when factually or logically wrong), you will be less likely to express alternative beliefs (even when factually or logically correct). In this way, social media propaganda not only serves to further an organization’s agenda but acts to suppress dissent.
This concept is not new. When I was in elementary school, decades ago, a friend used to get a group of kids together and then go up to an unsuspecting kid and tell a “joke” that made no sense and was not funny. But all the kids who were “in” on the deal would break out laughing – as would the unsuspecting target who succumbed to instant peer group pressure. Social media is the same idea, but on a global scale.