How is this not proving his point? Your whole comment is you bragging about how you arbitrarily decide that someone has nothing worthwhile to say based on an in group/out group dynamic that you created. It might not be needlessly hostile, but it is arbitrarily hostile.
Maybe it’s the opposite of your experience because you lack the self-awareness to realize that people who always play by in group/out group dynamics are who he is complaining about, despite how mature they consider themselves to be. They still act like cliquish high school girls.
Not really.