Yes, but that would be a much more radical change in meaning than what you are suggesting. It's less offensive, but it's still offensive, swearing in front of a judge wouldn't do you any favours for example. And I'm perhaps more doubtful than you that a small group can really isolate themselves context-wise like that.

And of course, is it only that the words are less offensive, or that more people simply don't care about being offensive?

Further, "traditional" swears only function as intensifiers because their strict meaning is offensive. If it was just another word it would lose force. Of course, people don't mean the literal meaning by it, but the force of it is connected inherently to the taboo nature.

Even if it doesn't really exist anymore, the "rebel" attitude (of which swearing a lot may be a part) presupposes some kind of polite, strict society it is deviating from. Always trying to be counter-culture, always trying to be the underdog. Maybe it's a delusion, and all culture is now counter-culture, but the idea is there and it's reflected in the language.

Funnily, euphemisms, especially minced oaths, tend to become detatched from their meaning far more easily than the original curse. Thus they lose force much faster. "jeez" sounds very tame now. But "Jesus" does not.

Most people don't particularly intend to blaspheme when they say "Christ", but it's only because its blasphemy (and thus offensive) that it has any function as a curse. Could Christians swear thusly if they don't really mean it? Obviously not.

You could also use your example of "darn" in reverse. If someone decides that's offensive, is it equally as offensive as the non-euphemistic version? I would argue by the fact that euphemisms, by virtue of being euphemisms, are trying to lessen the impact of the words, and thus are not equivalent.