As the photographer - I can assure you that the original logo on both the shirt and hat were pure black. The FD 135/2 fringes like CRAZY, and the ability to remove it quickly now is frankly awesome.Purple fringing wouldn't have turned an entire solid area like the logos on the hat and shirt purple.
It is combined with a selection tool - defringing is now added to the Brushes adjustment selection ability. Best to do the global defringing with the selection, and then paint out any areas where it may cause artifacts using the brush.If they can combine this with a selection tool, so it's applied only to specific areas of the image, it would be brilliant. Maybe in LR 5.