First, some definitions might help. In the narrow sense a "curse" is an expression that calls down ill/judgment, either on someone else, or on one's self, as when ta
…king an oath, such as, "If I am lying, may I be struck dead on the spot!" (The opposite sort of speech is a blessing.) So the original "curse words" would be those used to call down a solemn curse. But in common speech we mix this together with other categories of "strong language" which one is either not supposed to speak (at least in certain settings), or to use with great care, including: 1) swearing - taking of a solemn oath (which may include or imply a curse if you break it) 2) profanity - often used to refer to 'crass language' or 'foul language', but it originally means language which dishonors, or treats lightly as "profane" [common, 'vulgar'] persons or things that should be honored as sacred. (In the first instance, this means sacred things esp. associated with God, etc., the name of God, as well as highly regarded people [such as a king].) If you think about it you can see how all these types of language are related and how, for instance, "dirty [vulgar] words" end up being called "cursing/cussing" or "swearing". Also, note that uttering a curse in a formal oath or swearing an oath is usually considered acceptable --IF done in the right context, with due seriousness. It is tossing such things around lightly (again, treating the special as common/profane) that is the problem. Anthropologists sometimes speak of "taboo" words -- words it is forbidden, even dangerous to speak. In some cultures the thought is that speaking such thing AUTOMATICALLY causes something bad to happen. In others the consequences are social. --------------------------------------… That brings us to the thing that determines what is "bad language" of whatever sort -- it is the SOCIAL understanding of the word, that is, what it means to OTHERS. Some respond to this by saying "no word is really bad, it's just that people TAKE it as bad". But this is superficial. After all, why does someone CHOOSE to use words they know society regards in this way? This is, in fact, how language works! What makes ANY word "good" or "bad" ? It is all based on the agreed upon meaning of the word in the particular language--the very thing that makes language possible. So it's not making the sounds themselves that is at issue, nor is it (usually) about what's in one particular person's head. It is that you CHOOSE to make sounds (that is, speak a word) that you KNOW are used to convey that particular meaning in the language you are speaking. Even those who object to others 'determining what I can say' understand this. Otherwise they would calmly, even joyfully, cuss out a small child or someone they love deeply. In the same way, "Fire!" is just a set of sounds too -- but if you holler it, willy-nilly, in a crowded theater, it will have an effect for which you are morally, and probably legally, answerable. The point is that language --ALL language-- is a SOCIAL activity. To carry out its function (communicating with others!) depends on people's sharing an understanding of what the symbols will mean. And so, it's not OK to simply use any word you choose any way you choose and claim "Well, I meant something ELSE by it". (MORE) 
