With respect this feels like a very limited and limiting understanding of “decency.” How do you suggest we determine who gets to decide what is decent and what is not. We might try to invoke something like “tradition” or “common knowledge,” but we should remember such things are often rooted in racist, classist, and/or sexist, etc. practices and histories.
This is a big country, that’s made up of diverse groups of people living in a wide variety of environments. It seems perfectly fine that some social codes and behaviors be determined regionally, locally, or by subcultures.
On a fun side note, I’d suggest the following book as an interesting way of challenging your thoughts on profanity:
global.oup.com/academic/product/in-praise-of-profanity-9780199337583?cc=us&lang=en&