I grew up in Santa Fe. My parents owned an art gallery. I worked a lot with Indian Artists, mostly Navajo. The artists selling lower end wares (ie sitting under the portico) would tell the tourists that it was sacred. The upper end artists selling their wares for $1000+ would say that was not really the case. It's art. They are making money off of it, they are sharing it.

But... Joe Ben, a fabulous sand painter who sold his sand paintings for thousands of dollars was once doing a "real" sand painting demonstration - the tourists huddled around taking photos and it was twilight. Joe was very very upset - a sand painting of the type he made MUST be destroyed before sunset and he couldn't get to it. My father (a man with no empathy whatsoever) managed to force his way to the front of the crowd and kick the painting. Joe was forever in his dept. To this day, I'm amazed that my father bothered, Joe must've been upset enough to break through my father's lack of noticing.
Anyway - they are two different things. Copying art from other culters that's out there and that you can buy from them is no different, IMHO, than copying Van Gogh or any other art.