Thank you. This is the central, most serious and most important, issue. Based on Munoz's last statement that completely contradicts his 2 earlier stances, United's lawyers know it, too. The Chicago Aviation Department knows it's in deep kimchi, as well, judging by its immediate statements disavowing its officers' actions.
Police are not empowered to enforce civil matters, period. I know you know this, but this is for the benefit of those who believe the issue is a case of "that's what you get for screaming like a girl." Aside from that being completely irrelevant, nonsensical, and more juvenile than the very behavior they mock, it's worth noting that said "screams" only occurred as Dao was being physically assaulted. It amounted to three short yelps. (Oh, but they'll argue, Dao might have gone on longer, if only he hadn't been rendered unconscious so swiftly. /s) But again, that's all irrelevant to the central issues of legality.
It's telling that Dr. Dao was not arrested. I have no doubt that the police would have arrested him if they could have plausibly ginned up something--anything!--after the fact to give them even the flimsiest cover to justify what they'd just done. My guess is the Chicago Aviation Police were called in under false pretense by a United employee, who summoned them to deal with a passenger who was a violent security risk, instead off characterizing it as the contractual issue it was. By all accounts, the dispute was was completely peaceful until the point where the police unlawfully intervened.
Great post.