Your recollection is wrong. United has admitted that excessive force was used. They’ve said nothing like this will ever happen again. Even their own flight attendants who watched the video blamed the thugs for slamming Dao’s face into the armrest. They said the thugs should have raised the armrest to its upright position. What more do you want—a reinactment complete with a concussion?
What I recall seeing is that he hit the armrest of the passenger across the aisle from where he was seated.
This video appears to confirm it.
So they are saying the police should have raised up the arm rest of the passenger across the Aisle from where Dao was seated? Why would any rational person think to do that? What about the ones in front of or behind the passenger across the aisle? Dao could have hit those too.
How about removing the entire seat, because he might have slammed his head into the back of the seat if he had just fallen a little further towards the rear.
This is Monday morning quarterback stuff. People saying "they should have done this, or they should have done that", all to stop someone who is acting like a jackass from getting hurt accidentally through his deliberate struggles with police.
There are probably a dozen ways that man could have gotten hurt resisting the police, and it is a sheer impossibility for them to think of and eliminate all possible ways in which he might have been injured.