That's not the law. When someone "asks" you to leave a place you have a legal right to be, and you refuse their request, you do not automatically become guilty of trespassing or fair game for violence. Lots of confusion in this thread between a civil request and a lawful order.

When someone asks you to leave their property, that means you no longer have a legal right to be there. The correct thing to do is leave and resolve your dispute with the airline in court.

It doesn't give the property owner the right to escalate towards violence if the person has not given you any reason for such.

The correct thing for the airline to do is call the police if necessary and resolve the dispute using the law.

I think you should in fact be allowed to physically throw someone out of your house/business that refuses to leave, without having to wait for the police. Avoiding this is easy, just get up and go.