“After Dao dug his feet in, all United did was call the airport police. Anything that occurred after that point was out of its control, and was the responsibility of the police department. I agree.”
If you make a false claim against someone, and then call the police to help you enforce your claim, and you have done so in a situation that calls for quick action, then YOU can be held liable for the actions of the police. And while Dr Dao may sue the police as well as United, it is likely the police will counter sue United as well; having been called in to support an action United should not have been taking.
What false claim? United revoked his boarding pass and he refused to leave. How is that a false claim? Don’t lie.