Regarding Vulgarity

Once upon a time, there was a pirate that spoke a bit oddly, "I do say kind sir, I feel you have fecal excrement in the place where your brain should be."

He was quickly made to walk the plank.

He happened to have a brother, who was also a famous pirate, "Hey there, bastard! You are as dumb as a box of rocks. Do you have poopy brains?"

He was quick across the plank as well.

The two pirate brothers, that now happened to be tasty snacks for the sharks that followed the ship, had an older, pirate brother, who happened to talk like this, "Harr! Ye scurvy dogs! Ye must all have shit for brains for forcing my loyal blood across ye plank. I'll gut the lot of you and feed your fuckin' entails to me pet parrot, Bob!"

Instead of making the third brother walk the plank, they made him captain. It is rumored that this captain became so infamous, that the term, "He curses like a sailor" evolved from, "He curses like the cap't, the best sailor ever to conquer the seven seas." I digress.

When writing, especially writing fiction, vulgar speech can actual help to define a character, without having to actually define 'the character'. There is almost an allusion quality to it.

That said, I also agree with the adage that a writer literally improves his or hers conquest of language, by learning how to write well without vulgarity being used as a coloring agent.