By that do you mean, why don't I bring up that Cruz is not eligible?
If he were not eligible, it would have been taken to the courts already. It hasn’t and that should tell you something.
If he is "natural born", then the same must apply to Prince Hamzah bin Hussein (the son of King Hussein of Jordan and his American-born fourth wife, Queen Noor) and Prince Albert (son of Prince Rainier III and Grace Kelly). Impossible to believe that the Founders would have endorsed such a loose interpretation of "natural born".