Reading old books leads one to some interesting surprises, on occasion.  It turns out that some of our earthiest vulgarities and profanities have been around for centuries.  I guess people don't change very much.

And I believe that's the answer to another part of your question.  Sure, cultural norms cycle back and forth, to allow more profanity or less, to accept different ones and start condemning some that used to be accepted.  But in my opinion, the notion is mistaken that the human race over the long haul is steadily progressing from bad to worse.  There've always been times and places where language was coarser, more designed to shock and dismay, and other times and places where people tried harder not to give offense.  Combine the changing willingness to offend with the fact that the words and concepts that shock vary from time to time, anyway.

Is it worse right now than it was when I was a kid?  In some ways yes, obviously; but in the matter of vulgar language alone, not that I can tell.  I was in high school then, and now I'm an adult, so I keep different company; that probably contributes.  The natural enthusiastic excesses of adolescence made high school seem pretty bad; adults usually learn better (not all of them, of course).  So even if language is getting worse, it could be that I haven't noticed it because my set spent the same time growing up, as it were.

An example of varying offense:  When I grew up, I was not allowed (and not often strongly tempted) to say words like "hell" or "damn".  Others you can guess at.  But "fart" was not one of the words I was taught to dislike; it just a word, sometimes a humorous word and perhaps not entirely welcome among adults but no one ever hinted that it was a bad word.  Imagine my confusion, then, when I married and discovered that my wife was offended by it.

Then there's "fanny".  Of course its offense lies in the fact that in Britain it means something different; still, any Yanks should be aware that it could earn you a thick ear over there if you use it carelessly.

Most of these expressions, I find, are obvious modifications of actual cuss words.  Nowadays people say "freaking" or "fricking" because it sounds as though they mean (forgive me) "fucking" while still enabling them to act innocent if called on it.  Likewise "dang it", "darn it", "dag nab it", "a mell of a hess", "heck", "geez", "holy smoke", "shoot", on and on.  I don't think all ejaculations are like that, but it seems to me the majority are.  "Sam Hill" sounds like it's in the same realm.

By the way, 11larravec, I didn't pay sufficient attention at first but now I notice you didn't say "vulgarity" or "crudity" but specifically "profanity". Did you mean that, or did you mean just offensive words in general?