I recommend nonviolent communication, the book and the practice. Teaches the ability to “translate” highly charged conversations into basic human needs and feelings.
The person swearing was a random 911 caller attempting to receive help; we can't expect every caller to know nonviolent communication, or to recall it in life-or-death situations. The person upset by the swearing was a 911 dispatcher; if they have involuntary triggers around language then a job that absolutely requires remaining composed while talking to frightened strangers is dangerously poor fit. And I don't think it would actually be good for the dispatcher to practice NVC - whatever its merits, it's not a process meant for rapidly transferring vital information.
Safety and emergency-response communication is an entire topic of its own, and emergency medical dispatchers already get specific training on how to achieve the goals of that work.
I've never been a dispatcher, but I have worked in on-site assembly plant tech support, and I've seen the problem with escalating interactions quite a bit. The way I approach it, people who call in are upset and excited about their problems, not mad at me. Other people heard the raised tone of voice and took it personally.