Some people believe using profanity in their writing makes their prose sound more realistic. They claim it's necessary for shock value. While that may be, I don't believe it's "necessary" in order to create a sense of realism, which is all fiction is anyway.
In my novel "Sweet Revenge," I have some pretty tough characters, but I don't have any of them using profanity, even when they are being beat up by a group of thugs, or by the thugs themselves, for that matter. The antagonists (thugs) swear, but I never use the actual swear words. I just say, "So and so swore," or something like that, which allows the reader to imagine the epithet.
I don't think it's necessary to show a person swearing in order to show his emotional state. That can be shown by what he's seeing, hearing, saying, but mostly feeling in his heart.
I was part of a critique group once that was supposed to be strictly for writers of young adult literature. A young boy (around 16 or 17) joined the group and proceeded to put the infamous "F"-word in every other paragraph. When I told him publishers of YA material probably would not accept that kind of language, he became even more profane. I complained to the moderator, but she refused to do anything about it, so I quit rather than read any more of his filth.
I know I don't like to read those kinds of words when I’m enjoying a novel, and I think a lot of readers would prefer not to be subjected to them either, if the truth were known.
I for one, do not believe using profanity in ANY book is necessary, adult or young adult. I've seen many books depicting bad characters who use profanity, but the author chooses not to use the actual words. I think it's sufficient to indicate that a character swears, or swore, without using those profane words.
As an example. I read "The Great and Terrible" series by Chris Stewart. I recommend reading this series and other "best-selling" books by Mr. Stewart as great examples of what I'm talking about. Mr. Stewart has some pretty awful characters depicted in his books, characters who swear and use profanity, but he does not use the actual profane words, choosing rather to indicate that a character swore, and leave the bad word up to the imagination of the reader. It works. I don't think anyone reading his books will think they are fake or phony. They're quite realistic.
Another example is Dean Hughes' books. He writes about WWII and other difficult subjects where profanity should be expected. But I can't recall a single profane word and his books are totally believable.
Certainly, it takes a bit more creativity on our part, but isn't that what we writers pride ourselves as being -- creative?
I think we can avoid using profane words and still be realistic. It just takes a slight bit more effort. In my mind, using the actual words in our writing cheapens our work and is the lazy way out, and what example are we showing our youth?