Earlier quoted context omitted.
So if it's United's fault, remind me again why the security guard likely lost his career over this?
Fault isn't exclusive; United could have acted wrongly in calling security (making it United's fault on one level) and security personnel could have acted wrongly once called (making it their fault, as well.) Heck, both of those could be true even with the passenger's actions at some stage also being wrong. The idea that, in any situation that goes badly, exactly one actor must be at fault and all others blameless is…
So remind me again why we are exclusively lynching United and not potentially other bad actors (passenger, security personnel)?