The Perspective of Mixed Martial Arts

Many people don't want to do mixed martial arts because of the workout and training it takes to compete. Another reason is that their afraid of getting knocked out or injured and many don't want to humiliate themselves by tapping out or submitting. I am a amature mixed martial arts fighter, many people get amused or intimidated when I tell them I study fighting. My friends say it's because I have broad shoulders or because I am strong and black. Many people wouldn't know that I always stand/walk straight and I always have a smile, supposedly I always have a grin or solid face. Would that really make me look intimidating? I am an outgoing friendly person, I'm funny and everyone loves me except the people I destroy. I have no enemies. I can't make enemies no matter how hard I try or is it cause I look intimidating?. But when I go to a public karate or mixed martial arts dojos/academy's, people stare at me in fear and know that I will Bring it.  I'm a average guy! (5'10-6'0) (215-220Ibs) and still the reigning Champion at light heavyweight and Crusierweight. How can I be so intimidating if I'm barely taller then anyone?! I look in the mirror everyday and wonder that question, how am I so intimidating and how can I be less intimidating. And I know I'm intimidating to many people when I fight.