Tho' long out west, I'm from metro NY, where Fuck is commonly used as a verb, adjective, noun, & qualifier. Very useful for emphasis. Yup, sometimes nothing but a good "fuckin' _________" will do for conveying intensity of feeling. I cheerfully engage in it. Some of my friends do so even more. If someone is very sensitive to that, I'm going to feel weirdly buttoned-up around them.
Some profanity in regular convo doesn't bother me, UNLESS it's routinely being used aggressively to intimdate, or demean, or start fights .

However- there are exceptions:
One, is that there are some occasions, where letting the profanity fly is just not appropriate. Anyone who can't keep a pretty good lid on it then has to learn how. Manners are to ease comfort levels & smooth things along, & that's a good skill set to have.

Another, is around young children. I'm not going to freak out if they hear an occasional curse fly out of my mouth. But really, they hear it enough places these days, & children must be civilized a bit to make their way in the world. It's best to encourage that they learn some restraint, mostly to give them a chance to develop a REAL vocabulary.

Which brings me to the last example...Plenty of adults haven;'t developed any decent range of expressive words at all... & they curse ALL the time. It's boring, limits the spirit, & takes all the ooomph out of a perfectly good curse like "fuck.". These folks need a hiatus from cussing, & an effort made to learn some new words.

Meh. I curse like a sailor so it obviously doesn't bother me. I DO try to tailor my communication style to the company I'm keeping (I curse a lot more when I'm hanging out with my gutter punk friends than when I'm at a Love Tribe party, for example) but words are words and if you're using them correctly to express cogent and interesting ideas then I will forgive a limited and vulgar vocabulary. I get much more annoyed by people who can only talk about one subject.

That wouldn't work to well in my life since I don't feel comfortable with that about my sons. Though I do have plenty of friends who swear. and I swear when my boys and people I don't know or people's parents or people who don't talk that way are around. The thing for me is...if you use it all the time you wear it out. It doesn't have any punch anymore. I think they work better as words reserved to show intensity of message...that is totally lost if every other word is fuck.

I have always prided myself on using as little profanity as possible. Also, for many years I worked with both the public, and with children, so it paid to use proper English, diction, and no foul words. I always got high marks from my customers for keeping my cool in the face of really difficult people or situations.

Of course, even I couldn't be a gentleman all the time, so now and then when I'd stub my toe or something, I used foreign words. German is excellent for cursing, but Klingon is better! Most people I dealt with knew I was making an effort to keep the air clean, and they appreciated it.

My motto has become, "Anybody can talk dirty. It takes a real man not to."

I think you really first have to look at what profanity is as well as the application in a social context for the terms and Phases.

Just for shits n giggles I popped up wikipedia
en.wikipedia.org/wiki/Profanity

The use of certain terms in modern speech is not only relatively normal in some subgroups and subcultures it is expected. In other structures it is not.

To me to demand a person not swear when it is clearly part of their mode of speech seems to me as arrogant and demanding as if they were to demand you tolerate it. Seems to me to flow both ways. To demand the change would be in essence prior restraint of free speech and profanity is considered protected speech. In other words yes legally you can tell a cop "Fuck you Pig"

If it is significant and important enough for him to modify his behavior then fine. Otherwise it is up to you to decide if he is worth you modifying what you consider obscene and or vulgar.

Me personally I use modes of speech based on my audience. If someone objects especially strenuously I am unlikely to modify my pattern <except for My Mom> Mostly because I have little use for those that are easily offended.

JSin

Poon - Personally I share Myriad's take on it, the content of what people say is more important to me than how they say it (not that I don't appreciate chatting with a silver tongued devil or someone who's a clever conversationalist). Not only do I enjoy and accept swearing, I actually really enjoy learning colloquial swear words and expressions. Of course, in Canada "fuck" tends to be used as punctuation by most people under 50 in most non-formal situations really. One wouldn't do it in front of someone's church going great auntie who's just made a "lovely" pea specked tomato aspic for Sunday lunch. And I'd suspect that in most office cultures it's unacceptable (but so is any non-bland form of expression!). That said, it's useful to be able to tailor one's behavior to the context one's in and to have a bit of social sophistication if you want to be able to travel in a variety of situations and worlds since there are many class issues associated with swearing - it's a very bourgeois preoccupation historically (and even today really) since it separates the working classes from the middle ones who aspire to climb further up the social ladder (or make sure those on the lower rungs stay below them).

Saying derogatory or sexist things is another matter - but then I'd prefer to know up front if someone's got issues with women or people not just like them so I'm not sure if you're doing anyone a favor by teaching him to hide these attitudes if he's got 'em. There's some basic respect that's at issue there, not just a matter of language (once again, it's about the content for me).

Ultimately, regarding your friend, if he doesn't care and want to change the way he speaks - even to pick up more women or to "fit in" which seems to be the point of trying to get him to change - then it's really up to him. If he's not interested in women who'd reject him for swearing or for being from the "wrong" class then clearly the swearing actually serves a useful weeding out purpose for him. My question is, why does it bother *you* so much? Do you think your friend is being misperceived? Or do you find his behavior embarrassing to you?