I feel throughout this we still underestimate the power of police unions and the organization of individual police officers outside of their formal duties with their departments.
To my eyes, it really looks that simple.
Additionally, you may be suffering under some misunderstandings with regard to the Stanford Prison Experiment -- long story short, the methodology is largely understood to be flawed at best (Source: https://psycnet.apa.org/record/2019-45337-001) -- and therefore the conclusions as well. That may have contributed to misapprehending the fuller picture (nationalism) for the narrower one (tribalism).
I remain open to any new evidence that authority figures within the Democratic Party are also describing the media as "enemies of the people" -- but until that arrives, I think we can agree that in this case tribalism has been subsumed into nationalism -- since tribalism is just the low-level building blocks of nationalism anyway.
The problem is more complicated than simple.
I'm just saying that I think you can draw a direct line between the shameless attacks on reporters the past few days, and the words spoken over and over again by the ostensible top law enforcement agent in the country.