What I don't understand is why people don't recognize the fact that they are creating the exact opposite reaction of what they intend when they do this.
This will in no way "protect their business". All it does is make people want to have nothing whatsoever to do with them or anything they might have for sale and thus totally destroys their business.
As mentioned by others, requesting nicely that mention be made of the fact that an item was designed by cxxxxx whenever showing or selling an item made from the pattern and even asking that a link to the designer's website be included, would be much more likely to create the business protection they are desiring and would be much less likely to create animosity. In fact it would very likely increase their business instead of driving customers away in droves!