According to the article, the frustration comes from the fact that there is more than one commercial space company in the U.S. and SpaceX is undercutting those

According to the article, the frustration comes from the fact that there is more than one commercial space company in the U.S. and SpaceX is undercutting those companies' efforts when it has yet to deliver on its own promises to NASA regarding astronaut to space station flights. The reporter may be playing up the controversy a bit, but he's probably right about NASA's other concerns about the direction SpaceX is taking.