OMG I never encountered swearing customers during my working career. So really I dont think I can asses the nature of working environment there and the types of customers. When I worked most xustomers used to be obedient more than the customer service staff (honestly, no jokes). And a very laidback work environment.
So I dont know how things work in estate biz and espeically if its fast paced where you wuickly move on to the next customer and find it too then probably need to be super sensitive to customers is not there. But incase of the kind of customers you mentioned, the best is to just hang up without response, isnt it?
But am glad to see someone who supports his staff more than the crazies