The real thing to fear here is the normalization of violence. Good perspective in the WP comments: "The truly shocking thing here is that violence - with the real possibility of serious injury - was viewed as appropriate in a situation that was purely logistical. The airline wanted seats for its own employees. This was not an emergency - such as a terrorist attack or a drunk passenger endangering people. The lack of…
Section 25 doesn't apply, they were not denied boarding. And I don't see anything in section 21 they've violated either. Their forced removal seems to be the airline violating their own contract, not the passenger.
https://www.united.com/web/en-US/content/contract-of-carriag...