User blog comment:B214/Question and Answers 2/@comment-187.209.0.247-20140225185340/@comment-24501441-20140225223412

It's because of how devils and fallen angels are seen by others that makes them untrustworthy, due to past actions. It doesn't mean that just because he's a devil he can't be a hero, but rather, devils, who are naturally greedy beings, don't normally choose to do the things that would make them heroes. He doesn't need a specific sacred gear to be acknowledged as a hero.

As for True Longinus. You think that if Cao Cao were to do something against DxD than it would reject him? There has been no description that it has a mind of it's own, but rather when in TRUTH IDEA FORM, it is the will of god and makes miracles. Plus, look at Cao Cao's actions. He and his team kidnapped a peaceful Yukai and drove it out of control to summon Big Red, attacked devils and an angel, who had done nothing while on a trip, took advantage of a crisis in the underworld to further their own goals, sacrificed HUMAN BEINGS in order to force some of them to awaken BB, used children as bait to attack other devils, and used a child as a hostage. What of those actions can be seen as being heroic? But Cao Cao still has Truth Longinus.