The court ruled that "trash talk was part of the creative process."
All in all, that's an interesting ruling. As the title of the post here says - and from the article - sometimes vulgarity is necessary in the job.
Now, let's think about public relations.

PR is stressful. It's supposedly a top-ten stress profession (an old WSJ story). It's always been a stressful profession, where the stress comes from three places at once: media, client and agency. Or, if you are in-house, it comes from the media, the internal people and the agency (the stress comes from running the agency).
So, what's a great way to relieve stress - yelling and swearing. Not at people, but behind closed doors, or when you hang up the phone.
Try it. If you have an office, next time you have a bad media experience, hang up the phone and say "go fuck yourself" - you will feel better. It's a little bit of stress relief.
Seriously, so does PR also fall under that "sometimes vulgarity is not just acceptable but necessary" - is it necessary for stress relief?
I know that the good swear sometimes relieves my stress. Yes, there are other ways to relieve stress (sex), but that doesn't work at the office.
And, let's be honest. A good PR person can weave profanity like poetry, where it goes beyond swearing to a new level of language. Because, that's our job: to weave language and tell a story. Sometimes, in profanity.