With an ORAC of around 1,000 it's not that white grapefruit juice is necessarily bad, rather it's just not the best choice when you compare it to others such as grape, pure cranberry (without added sugar/juice sweeteners), or even canned prune juice which gives you double the amount.
ORAC Source
USDA Database for the Oxygen Radical Absorbance Capacity (ORAC) of Selected Foods, Release 2 - Prepared by Nutrient Data Laboratory, Beltsville Human Nutrition Research Center (BHNRC), Agricultural Research Service (ARS), U.S. Department of Agriculture (USDA) - May 2010