According to politifact, me and DW are correct about this. Whatever politifact is worth, it's a good read:
United passenger had every right to stay, Fox analyst says
Timothy Ravich, an aviation law professor at the University of Central Florida, told us passenger rights are still limited by laws, regulations and policies. Airlines have the authority to decide whether passengers are breaking the rules, and can remove people at a company's discretion, even against a passenger's will.
"The suggestion that Dr. Dao had ironclad rights merely by buying a ticket, passing through TSA security, and being in his seat is incorrect," Ravich said.
Notice it says AIRLINES have the authority to decide this. They make the rules, so they can decide if you're breaking them. As soon as he refused to disembark the plane, he was breaking the rules. At that point he lost any rights he has, except the right to remain silent. He violated the contract of carriage. There is a reason no lawsuit has been filed. It takes an hour to file a lawsuit, not 2 weeks. He can't find a lawyer to jump on this and we all know why.
It's the same as if you came to my house and I handed you a contract of rules you had to follow at my house while here. If I decide you broke a rule, I can remove you from my home. I own the home. You can't run and get a lawyer and sue me. I make the rules, I enforce them. United made the rules, United enforces them as they see fit.
It's a free country, he was offered 4 times the price of his ticket to leave. He refused, so he was removed. If you pay me 20 dollars to come fish in my pond and I ask you to leave by offering you 80 and you refuse, I can then have you removed. It's fair.