I suspect the tendency is to revise "Western" to mean redneck (i.e., racist) and/or the violent strong man theme, which is notoriously close to some Fascist esthetics and philosophy. Which, incidentally, is why I suspect a strong overlap with the Christian DVD market.
Well, that's exactly what you did in your first paragraph. You were more right when you said that Westerns went against the stereotypes. I've recently been re-watching some old Lone Ranger
episodes and many of them deal with anti-racist themes, both in terms of the Indians and Chinese immigrants. They may be considered simplistic or naive by some people today, but they are good-hearted. As for the dearth of Black characters, Westerns were no worse than other shows or movies of that era; it was a sign of the times, not a characteristic of the genre.