So, don't buy that game, or if you want to use a Wii for homebrew, buy another for games. Nintendo isn't stopping you from modding your system. They simply say that if you want software upgrades, you have to accept their terms.
It isn't like they load it in the background. It isn't like they don't tell you what they are doing. It isn't like they don't give you the option to keep everything like it always was. This is pretty tame compared to other companies' tactics to combat piracy, and I see nothing ethically wrong with it.