I have advise my relative of the above. I also opined that one option is to give the elder a card with his/her cell phone on it. If he IS "compos mentis," s/he can let him know he can call for help any time. If he is savvy he may be able to learn how to disengage when the mooch is in the buildup phase of a verbal attack, retreat to a safer place, and call.
At that time, my relative can call the relevant agency for help so that THEY will catch the abuse in action. In effect, let the abuser hang HIMSELF. Just imagine the prospect of the mooch, all wound up, trying to drunkenly explain to the cops what an asshole the elder is. :~) Then he'd be not only abusing (misdemeanor or felony), he'd be drunk and disorderly, with either a blood alcohol level or a field sobriety test ON RECORD. If they get enough calls like that, THEY will establish the mooch's pattern. Perhaps the elder's blood relative will get tired of bailing his ass out of jail.