 Why can't the square-built man defend Trella against the men attacking her?
Trella feared she was in for trouble even before Motwick's head dropped forward on his arms in a drunken stupor. A woman could not possibly make her way through these streets alone to the better section of town, especially one clad in a silvery evening dress. Perhaps she could call one of Motwick's friends; she had no one on Ganymede she could call a real friend herself. Trella swung with her whole body, and slapped him so hard he nearly fell from his chair. Her protector was obviously unwilling, but the dark man, faced with his massiveness, took no chances. The dark man moved in on Trella again as Kregg overtook his quarry and swung a huge fist like a sledgehammer. Exactly what happened, Trella wasn't sure. She had the impression that Kregg's fist connected squarely with the short man's chin before he dodged to one side in a movement so fast it was a blur. But that couldn't have been, because the short man wasn't moved by that blow that would have felled a steer, and Kregg roared in pain, grabbing his injured fist. The dark man, who had grabbed Trella's arm, released her and ran for the door. Trella ran to the unconscious Motwick's side. The gravity of Ganymede was hardly more than that of Earth's moon, but the way the man picked up the limp Motwick with one hand and tossed him over a shoulder was startling: as though he lifted a feather pillow. He followed Trella out the door of the Golden Satellite and fell in step beside her.
 His programming does not allow it
 His programming does not allow it  He is a strict pacifist  He is full of cowardice  He is secretly collaborating with Trella's attackers