I think you can pretty much summarise this whole incident in one phrase
'The Death of Common Sense' which was the title of a book published in the US in 1994 and on the first page has the comment
'The book provides numerous examples of how bureaucratic rigidity, costly and ineffective regulation, and overly complex procedural rules have superseded good judgement and common sense'
Whwere was the common sense from the gate staff realising there would be a problem with 4DH staff
Where was the common sense among the cabin crew before claling the cops
Where was the commons ense among the law enforcement officrs
Where was the common sense again among the cabin crew wehn this degenerates intoa bleeding man being dragged from the plane
Where was the common sense from the Flight deck who must have been aware of the kerfuffle down the back -it must have made alot of noise and surely the In chrge had to tell the Captain the cops were coming
Where was the common sense in UA management about flexibility when DH crews were being boarded- don't UA aircraft have a jump seat which one of them could have used allowing Dr Dao to keep his seat.
The answer of course is that it is really dead suffocated by processes, procedures and regulations which punish severly anyone who infringes them even if they are doing the right thing.
A story for our time