What a concept – a boarded passengers can now keep their seats. Remember that the initial reaction by the CEO was to stand behind their people and decisions (unwavering). 

I agree the dude should have got up when the officer asked, but broken nose and lost teeth? Excessive. They guy is 60+ as well, should have been treated better. I mean threaten to stop the entire flight and have everyone leave the plane. The group pressure would work on a normal person.

Regardless, you there are other major procedural issues here. I mean why are they allowed to break what is perceived as a contract to have a seat and fly?

Turns out the United issues are the tip of the iceberg. Many FAA rules were written to favor airlines like the pushing folks out of their seats. 
Too little too late. United first impression on this epitomizes their focus on cost control at the expense of customers. 
https://mobile.nytimes.com/2017/04/16/us/united-passengers-removal.html