I agree with what Blabby says, up to the use of lethal force if necessary, though all violence should be avoided if possible. I think we have a moral duty to defend those who are weaker than ourselves from either verbal or physical abuse.
Maybe it's some kind of cowboy thing, but bullying those who cannot fight back is behavior I won't tolerate in my presence. I would ask you to consider the feelings of those old people who felt intimidated--people largely unable to defend themselves. Since all people are perfectly within their rights to do what it takes to defend themselves, the alternative is that people will either start getting CCL's and packing, or they will avoid those places where they don't feel safe. Nobody wants to be harassed, physically intimidated, or worse.
When I first took over my library, there was a bully who used to come in there and try to chase people off the single Internet terminal. He would stand behind them and make snide comments and veiled threats. I understand that growing up he was a decent fellow. But he suffered a head injury (diving), and became meaner than a snake.
I confronted him after I caught him bullying an old lady, and talked to him alone in my office, and threw him out of the library. Well, he became belligerent, and I called the police. It was a matter of staring this bully down and listening to all sorts of insults and verbal taunts until the police arrived. Although he never made direct threats against me, he was under indictment for threatening to kill a judge. I never heard from him again.