> It shows a lack of vocabulary more than any sort of moral failing.

Here, now, I call nonsense on that one. I (probably?) swear more than most of my friends in private, casual communication circles. I also have a much greater vocabulary than any of them (this is not hubris --- I'm frequently told to explain words I use; I chalk this up to being better-read throughout my life). It just doesn't follow that because a person favors certain words, that they must not understand or feel comfortable with others.