I cannot imagine the Apostle Paul in his missionary work addressing sailors and ruffian tradespeople the same way he would address the Jewish Sanhedrin.
There are degrees of vulgar ( or common, lower class speech ...). Exclamatory, Defamatory, and Excretory ... and of course Sexual.
Some people are so used to coarse, vulgar speech that if you do not speak like they do ... they do not even HEAR you ... you are immediately dismissed as a Wuss.... a cowardly effeminate man lacking male genitalia.
Paul said he was all things to all people .... in the area of communications.
However .... I remember years ago, after a particularly good talk at the Kingdom Hall, I got up and excitedly exclaimed to the Sister behind me "Wasn't that a HELL of a good talk ?"
She looked at me like she had just been shot in the back with an arrow.
Clearly a case of me not "knowing the audience".
.... by the way .... looking at the Clint Eastwood movie "Gran Torino" is an excellent reference to see this linguistic cultural norm being taught a teenager, as a survival tool.