An interesting theory about why this 2016 primary has been tough on social media: we assume our friends agree with us and are surprised when they turn out not to (and sometimes react badly to that).
As with so many modern relational ills, much of the problem lies with the internet. It’s not just that people tend to be more obnoxious online than they are in person. The primary is revealing rifts among people who are used to assuming that their friends agree with them. Ordinarily, social media users who talk about politics congregate in polarized communities. Particularly on Facebook, they expect to revel in a shared sensibility, not to argue. “We find that our participants who perceive more friends as holding viewpoints different to their own engage less on Facebook than those with more similarity in their network,” says a 2014 Georgia Institute of Technology study about politics and online relationships. (The italics are in the original.) This primary—the first Democratic one since social media has become ubiquitous—has shattered the illusion of bien pensant unity. (Source)
Being surprised by disagreement leads to Anxiety of Peer Influence