In combat, you cannot worry about the educational background, religious background, economic background, race, nationality, etc. of your attacker. You must have a combat mentality that can channel destructive forces that exceed those of an aggressor. You must be a cold, vicious animal; free of sympathy, fear, anger, apprehension, and ego. You must possess killer instinct.
Some martial arts do not stress, or even discourage, a combat mentality. It is concerned uncivilized and barbaric. For some, it violates their religious and philosophical beliefs. Others replace it with a competitive, sport-oriented mentality that lacks the brutal and aggressive characteristics necessary to neutralize a crazed criminal attacker.
Everyone has a killer instinct. This is how humans have survived to this day. It is stronger in some than in others. In less civilized times, those without it did not survive. Now, we protect them and they try to justify their inaction as being the "right" thing to do, at least until they need protection, then they want the ones with the killer instinct, the warriors, to protect them. Some manifest the killer instinct inappropriately in blind rage or haphazard fury. They are driven by a raw killer instinct that is inferior and undisciplined. Their energies are poisoned by emotion, resulting in poor techniques and tactical errors.