A very interesting question. You are right that most swearing is either sexual (F~) or religious (God!, what the hell). Christianity has been in slow decline in Britain since about 1870, more so since the 60's, but I'm not sure more blasphemous swearing had declined with it - possibly the opposite. Why does nobody ever say Oh Buddha!?
There is an awful lot of culture in this, and the Victorians clearly were very prudish, unlike previous generations. Were Chaucer and Shakespeare really bawdy and (c)rude or was the use of literally more Anglo-Saxon words simply accepted as normal? Did the Victorians take offence at what was actually just plain speaking?
The bible doesn't contain a list of words you ought not to use, the nearest I think would be Neither should there be vulgar speech, foolish talk, or coarse jesting/crude jokes —all of which are out of place—but rather thanksgiving. Sometimes it is obvious when vulger and crude speech have crossed a boundary, other times less so. What is the intention of the speaker, and are the listeners being over-sensitive.
I don't like people's sincerely held and reasonable beliefs being ridiculed, if only out of respect for the people, nor do I like expressions that are demeaning about a person's sex. This can end up being verbal abuse.
Since I don't believe in a right not to be offended, I have tried to develop a fairly thick hide on the language some people use.
Swear words are called expletives because they don't add anything to the meaning of the sentence, and there is no real need ever to use them. I remember seeing the film Phone Booth in English, and the f word seemed to be in every other sentence. It wasn't true to life, wasn't necessary, and became boring and tedious.
