Probably, just as anyone would be if they decided to change Shaft or Blade or many other non-white comic book heroes' race.
The thing is, regardless of your view of Singer or his Superman movie, he said it right when he stated Superman should step out of your subconscious. I've known Superman's appearance since the time I could remember, and he has been white. That's the way I remember him and that's the way I want to see him because I remember him that way.
Making him another race to me seems just the opposite of color blind. It seems very deliberate like instead of trying to nail the character and his widely recognized appearance, they're trying to fight taboo or make a statement.
This whole color-blind casting is a idea that will never be accepted, by ANY parties. Race is too embedded into our minds as a great source of clash, misunderstanding, and lack of communication. There are too many people on both sides and all sides that cannot look past color.