...standards of vulgarity being audience dependent.
True. And those standards are dropping like flies every day.
(sigh)
If you mean there is a lowering of the standard of showing respect for others by avoiding vulgarity I agree with you. But what I meant by audience dependent was the standard of what is actually vulgar and how vulgar, and that has to do with social setting, and thus for an individual spending time in one society and then another it may fluctuate up and down.
For example, sailors may cuss freely out at sea without anyone's sensibilities being shocked at all. But take those sailors and put them at a formal setting at table with the Queen of England, and they will realize they ought to change their language--although they might inadvertently fail to do so because of habit.