I think it has to do with numbers plus the spread of social media creating an irrational sense of entitlement toward characters/actors. When Supernatural was one of those shows that people thought would be lucky to last 3 or 4 seasons, fan discussions were a lot of fun to join in. Then it blew up, and crazies came out of the woodwork. This was my first time encountering a ship war, and it was so overwhelming that it was hard for normal folks to try calming fans down when they went after each other. The amount of vitriol aimed at Ackles's wife because she ruined some fantasy rabid fans had made up in their minds just made me give up on engaging with them completely. I'm actually glad that the show itself pissed me off enough to drop it years ago, so I'm not even tempted to check and see how bad Supernatural's fandom is nowadays.