Here's some background on the company:
A Leader in Manufacturing
Comment: I'd say the problems fall into three categories.
Adrienne notes how Ed Ismert learned "all about" the Sioux from his father Martin, another white man. And how the description of them as competitive and fierce, yet deeply tied to the earth and the Great Spirit, is stereotypical.
These things don't bother me too much. I don't think Ismert had to be an expert to apply the Sioux label to a plumbing supplies company. And the description of the Sioux is balanced, at least. Many people describe Indians this way, including Indians themselves. And generally speaking, I'm not sure the description is wrong.
As Adrienne observes, the description is entirely in the past tense. The company doesn't recognize the Sioux's continued existence. And there's no such thing as a singular "Sioux Indian Nation." The Sioux consist of Lakota, Dakota, and Nakota people separated into independent bands or groups.
Associating a Sioux chief with plumbing supplies is an insult to Sioux chiefs. It's like naming your company George Washington Plumbing Supplies or Virgin Mary Plumbing Supplies. You could do it, but you'd look silly and so would George or Mary.
Needless to say, the company has no actual connection to the Sioux. Choosing the "Sioux Chief" name is like naming my company Acapulco Señorita Comics because I consider the books hot and spicy. I doubt anyone would accuse me of fraud or deception, but the name is clearly misleading. The comics have nothing to do with Acapulco or señoritas.
Like most other misuses of the Indian chief, the name is an obvious ploy to make the firm seem noble, dignified, and honorable. To increase its authority by somehow tying it to America and the land. A Missouri company started in 1957...but we're supposed to believe it's as ancient and timeless as the buffalo or the Rockies.
Basically, Sioux Chief perpetuates a common Native stereotype for no good reason. Thousands of products--Pontiac cars, Indian motorcycles, pemmican packages, oyster cans--do something similar. In most cases, the association is undignified, unjustified, and stereotypical. We've eliminated products named after black Sambos or greedy Jews, but savage Indian chiefs are still okay.
For more on the subject, see Hiawatha Trains and Logo and Military Craft, Cars, and Liquor.