2) take the word "fuck" for example. I don't find it offensive in the least. It's a fascinatingly versatile word. If someone stubs their toe, and shouts "fuck", I am not offended. If someone looks me in the eye, points their finger, and says, "fuck you", I am offended. The word is the same, the context is different. The offense seems therefore to be derived from the context, not from the word.
3) No, again back to point #1. The presence of someone's offspring, in no way can or should obligate me to follow their moral values. Asking me to refrain from swearing because of delicate children's ears is someone imposing their moral code to determine my behavior.
I 100% agree with your last 2 paragraphs. I alter my language depending on context, anyone with a modicum of social skills does that. I was just responding to your original individual bullet points.
To add a little levity, I recommend everyone watch the YouTube video about the versatility of "fuck". Of course, please use headphones in order to not offend anyone around you. (sorry, had to be slightly tongue in cheek there -- hope you don't mind me poking a little fun)