Another good article Jon.
Control: I have always found this interesting and it is passed down through generations. I have a list in my head as to why people yell. It is learned behavior and it may be a twisted sense of control or reward. It is about the person yelling and may be an emotional response or now habit leaving no explanation. Some may not even realize they are doing it.
Maybe as a thread we can make a list of circumstances or experiences and each person can state one of them. It would be a good engagement exercise.
I have a note to self-list in my head I have acquired since childhood of these experiences. Caught off guard it can still bring me to tears as I definitely did not understand.