As a pilot, the author should know that Dao was not interfering with a crew member, because the flight attendants did not become crew members in law until the door was closed (according to 49USC§46501) and/or the aircraft was moving under its own power (according to 14CFR§91). Yes, it's silly, and counterintuitive, and even contradictory. Welcome to law. This is the law that United's defenders keep trying to invoke, but they clearly do not know what the law actually says or means. It's an appeal to an authority that doesn't actually support them. In other words, it's BS.

The point about the deadheading crew is more interesting IMO. It's their arrival that triggered the whole thing. Why were they so late arriving? Did United's logistics screw up by not putting that crew on another flight, or did the crew themselves screw up by not showing up for it? United still hasn't clarified. It is perhaps worthy of note that the deadheaders were the only ones here who were United's responsibility; the rest (and worst) of what happened was on either Republic or Chicago aviation security. United might be faced with a choice between admitting their own direct responsibility for causing this mess vs. having to explain to AFA why they threw union members under the bus. Silence might seem preferable to either of those.