Let's also remember that David Dao was physically assaulted, which is a separate matter and that cop should be charged for the crime of using excessive force.
He was told he'd be removed forcefully and the man said he didn't care. He was removed forcefully with adequate force.
They literally just pull him from his seat. I don't know how else you would forcibly remove someone whose resisting getting out of their seat.
Going by literal definitions, an officer tackling a man out of the way of a bus would technically be a "physical assault". But if your headline was "Officer physically assaults man", people are going to have a much different impression.
Tell me whats wrong with pulling a man out of his seat when you are ordered to remove someone from a seat and that person refuses to leave peacefully.