Isn't it more that the words that are acceptable are changing?

In the ancient past, it was "taking the lord's name in vain" that was so extreme. Now, most people don't care about that. You can still see that difference in the "curse words" used in Quebec vs. France. In Quebec the naughty words are all Catholicism-related: esti, calise, tabarnak, etc. In France they're more similar to the common English ones: merde (shit), putain (whore), etc.

The religious swear words had lost their bite in most English cultures ages ago, people still say things like "christ" or "oh my god", but those mild expressions would have been jaw-droppingly awful a century earlier. For a while damn was one of the most awful words, which is why you had things like "gosh darn".

Now, it's words that were truly offensive maybe 40 years ago that are becoming common: fuck, shit, cunt, etc.

But, at the same time, words that were common in the past are becoming truly offensive now, for example "the n word", faggot, retard, tranny, etc.