-the crazy part,they're all senior citizens
Conflicts at the field will almost always involve seniors. It could be the onset of degenerative neurological disorders. I don't know what you call it. They may appear to be very stubborn or unreasonable. But I believe it is a symptom common to several diseases.
There are no physical or mental requirements to fly models. Considering the energy and force with which one of these models can strike a person, I would conclude the party exhibiting such behavior is dangerous to himself and to others.
Although we should not make club rules forbidding mentally/physically ill members, we should have rules pertaining to behavior. Such rules would help protect ourselves form people that should not be flying.