As I said at the time, I probably would've done the same as Dao (except hopefully the high-pitched screaming).

Here is an article written by a law professor at Cornell who discusses the contract:

For the moment, I want to focus on the basic premise—and legal assumptions—behind most of the press accounts of the incident.

Most articles and news reports have implied that the airline was permitted to remove Dao from the airplane. Articles have made this claim as part of a larger point to readers: Airlines frequently overbook their flights and “bump” passengers, and then pay them compensation in line with federal regulations governing the payment of this compensation.

It happens all the time, according to the newspapers.

This overarching narrative—repeated in virtually every newspaper, with only a few exceptions—is incorrect at least as applied to this situation. Or, at the very least, it is far more complicated than the news reports suggest.

https://www.yahoo.com/news/why-united-legally-wrong-deplane-134223391.html

This article is a few days old but I haven't seen it discussed yet on CB.