As to being public places, even the mall, the theater, the library, etc., have certain expectations of conduct. If a person is disruptive, destructive, acting dangerously towards others, the owners have every right to call the police. While the "public" is invited, certain conduct is expected.
The elders have been instructed not to physically try to make anyone leave but to call the police and let them do it. If a disruptive person hits someone, then they can protect themselves. But it is best to try and not be confrontative.
If a person has visited a KH in the past and been disruptive, I can see why that "public" might not be let in.
In 50 years, I have seen the police summoned 3 times, once for a drunk non-JW on the doorstep, once for a man yelling and screaming in the auditorium about his wife studying with JWs (twice).
If these people had come to my place of work (which serves the public), the police would have been summoned as well.
Now if the person(s) has always been well-behaved at the meetings and is barred, they probably have a right to be there, but why bother. Just go to another KH. (I understand that this does not cover every situation.)
Blondie