Whilst I agree, to a point with what you have said, you are still using words that might be offensive to someone around you; it is your duty to sugar-coat obscenities unless you personally feel that there are plenty of other words that you could use instead of the tired four letter words, which are far more descriptive.
I would still 'play it safe' though, by not using words that might embarass anyone within my hearing range - that is, as I see it, out of respect.
Up until very recently I felt exactly the same as you Michel. That is to say that I felt it was my duty to ensure that people did not take offense at what I said EVEN if no offense was intended in my words. However, the difficulty for me came when I tried to reconcile this idea with 2 things that have become central to my philosophy now.
The first of these is the Golden Rule. If I am changing my language for others benefit then I must expect others to do the same for me. Yet I really don't expect them to do such a thing for me because it seems totally unfair on them. Its one of those cases where it seems like I am asking too much since I am asking everyone to act as a crutch for a problem which is essentially my own, my inability to deal with certain words. So if I can't expect others to do this for me then I shouldn't do it for other people if I am to stay true to myself.
The second is my belief that I should only help others to help themselves. I justify this on the basis that otherwise I will create a crutch for them, out of myself, leading to a false sense of security on their part, which can only lead to disaster. By sugar coating my words I am essentially doing this for them because I am helping them to avoid rather than deal with a problem, albeit a minor one. If they don't deal with this problem then they will be unable to interact with people who aren't prepared, and fairly so, to make a crutch out of themselves leading to intolerance on both sides, which, as I'm sure you are aware, is my biggest no-no.
Having said that I can totally understand your point of view and I think subconciously I still do the same as you because it has been ingrained in my way of thinking for so long. One major exception to this is swearing around my parents. I have now managed to desensitise them to swearing so they no longer are offended by it simply by swearing excessively around them. For me this is a vast improvement on me having to watch what I am saying around them for fear of admonishment.