I'm continually stunned by what good actors people in everyday life are, especially when they don't believe they're playing a part but believe in the images they're trying to project to others. Compassion is a [crucial pasrt of GT's self-image. Without it, his legitimacy falls apart, interanally as well as externally, and all his actions would come racing at him without his usual rightous insulation from them.
Also, I think this area is just a personal interest for him. It's his version of tinkering at the workbench in the basement. He doesn't need to care abouyt the people involved, battling evil is fun.