Whether the flight was overbooked is irrelevant. Even if Dao had been the only passenger on the plane, when the flight attendant tells you you have to get off, YOU HAVE TO GET OFF. It’s the law.
Police have a saying, “You can beat the rap but you can’t beat the ride.” IOW, if they come to arrest you, you aren’t going to talk your way out of it. They don’t have that leeway. So shut up, get in the car and call your lawyer after you’ve been booked.
The same applies here. Don’t argue with the FA, take it off the plane and voice your objection to the gate agent.
"Arrest" is a legal term of art. The police do not arrest everybody they detain, and they do not detain every person they "encounter."
Agreed though, noncompliance with police orders or "requests" can result in escalation to the use of force. Without some tactical force advantage, it is foolhardy to offer even passive resistance.