I think that the words have a violent nature to them. They're not always spoken forcefully in anger, but they are designed for it and carry that feeling with them. You won't hear any five-syllable swears -- these words are short and to the point, meant to be spat out. I tend to flinch when I hear swear words, so I can understand how JWIQ feels.
I agree they are short, sharp words that intensify a sentence. I disagree that this is what they were designed for or that they have a violent nature (although I'm not sure how a word can have a violent nature...). Originally these words were normal words that were a normal part of our language. The classic example is the many roads in the UK which are named GropeC* lane (or were, they have almost all been changed now). This word was on our roadsigns! I completely understand the flinching though, I appreciate that things are different today. The question I'm asking is why these words. There thousands of short sharp words that can be viciously spat. Why do we pick on these? (my theoretical answer: because of the Normans!).
This is a bit ironic since I do swear in private, but the difference is that I am expressing my anger while others are not around. Having someone else say them to me is a bit like being swatted in the face because of the power of the words. I think it's better for relations with other people if we moderate our expressions when talking to them instead of going full-bore, and most people do indeed moderate their emotion when interacting with others, including toning down their speech.
This may just be a bloke thing, but I've noticed that the closer knit the group is, the more they hurl abuse at each other. :) It's not to upset the other person, the swearing actually intenstifies the group bond. It says "look, I can say these taboo words to you and it's ok!". It's also pretty much the only way straight men have of saying "I love you man."
At the very least, even when the swear words are not making me flinch, they at least tell me I am dealing with someone of a lower social standing. Strangers simply don't use words like that with each other where I come from. Among friends, of course, we speak in a way that we know they're comfortable with, and some groups of friends think that swearing is no big deal.
... and we're back to the Normans again! Sitting in their castles and despising the lowly Anglo Saxon peasants working in the fields. Here's another example of how our language is keeping the tyrannical boot on the common mans neck. when it's on a plate (in the castle) it's called Beef which is a French word (Norman). When it's alive in a muddy field it's called Cattle which is an Anglo Saxon word. It's the same for Pork (Swine) and Mutton(Sheep). Our whole language is one of social tyranny! (it's not really, I've gone too far).
Anyway, arguing over the denotations of the words is not useful because we these words have been given a taboo nature. We can't be expected to throw away centuries of cultural conditioning and use them like any other words. It's a faulty argument which pretends that words don't have connotations, and it's a line of thinking that no one follows when actually choosing their words carefully during a conversation so as to avoid giving offense.
Why can't we throw away centuries of cultural conditioning? That's what the Suffragettes did! Instead of burning our bra's let us burn our dictionaries!!
(I've definitely gone too far now!!)