He gave the engineer a small glare at that comment. Steve knew that Stark had his reasons for being wary around Bucky and he knew that they were legitimate reasons, but he couldn't stop himself from being upset still. "He's not going to hurt you again, Tony."

Steve believed that Bucky wouldn't hurt Tony anymore, especially since he was helping him with the arm. Additionally, Bucky seemed to listen to Steve about a lot of things and he told him not to attack. He felt a little bitter that he had to 'order' Bucky around, but he didn't want anyone hurt.