I could not agree more with this - this has been my theory for a couple years. I'll also say the mods here are extremely tolerant of such behavior - much more gracious than I would be!
A while ago I got to thinking about this, because it really does seem to be pronounced among Kings fans - the persistent extreme negativity, it's beyond a typical beleaguered Cleveland Browns fan for example. I reversed the causality as a thought experiment: what if it wasn't the team making the fans negative, but the fans being negative in their own right. This made much more sense, because as we began to get good over the past couple years, and a legitimate light at the end of the tunnel began to appear - that light seemed allergic to some fans - who may or may not happen to post here occasionally. At that point it became clear to me that over the years the Kings has attracted some fans with a really negative mentality, and they were merely using a bad team as an excuse to look at things negatively. Doesn't quite work as well when you have actual hope and the team is objectively becoming good.