Interesting article and like you said worth the read.
I wonder if the cause of the contempt stems from the focus/imbalance of "uniqueness', "specialness", and customization/convenience obfuscating the overarching "Team" that is the the U.S. (In my case); essentially turning your neighbor or anyone that doesn't share one's deeply internalized and over-personalized beliefs into "The Other".
Also the ability to customize your reality and turn any information feed into an echo chamber can't help either, I would think.