Here's a nice informed version of what happened on the airplane by passengers on board.
When the United attendant went around "randomly" choosing people to kick-off, two other passengers were approached first to which they refused and then the attendant moved-on to the Dao to which when he refused, they called for the police and...
Normally when you have a so-called hostile passenger, everyone on the plane hates him or her. In this case all the anger is towards the airline. So it contradicts the United Airlines version that Dao was hostile after being treated politely by United personnel.
Was United Airlines CEO Oscar Munoz today quick to directly apologize to Dao after blaming him before because of the firestorm on the internet in China calling for a boycott? United Airlines has 20% of the routes to China from the US, largest of the US carriers. Also United is privileged with having routes to 2nd tier Chinese cities.