"I think that perhaps very squishy subjects like politics are particularly vulnerable to this sort of disconnect, where a complex viewpoint is formed based on the hot topic of the day, and this viewpoint persists for years or decades even if the basis for its formation is completely forgotten."

Not only disconnect: What I've read of psychological studies indicate the mind amplifies those facts that support it's current model of the world and actively ignores those that do not.

Which goes a long way to explain why it's nearly pointless to argue with fanatics of one kind or another.