I personally don't swear, but I don't have a huge problem with others using mildly colorful language around me (I have problems with some of the harsher 4-letter words, however). The reason these words are offensive though is primarily because of their definitions, though there are also large social connotations to them as well. We never hear, say, the f-word used in a pleasant way; it is always used when trying to explain a rather tasteless or unfavorable idea.
Besides, I feel that swearing hinders communication, because rather than try to explain how you feel, you merely say, "Oh, ----!" It is a lot easier to throw out some off-color word than to express in detail what you feel, and you fail to resolve the negative flow in your head: instead of breaking down and resolving the negative thought processes through constructive dialogue, you push them aside. And kids don't need to resort to this at an early age, when developing communication and critical-thinking skills should be of great concern.