At first Mike didn't really think much of Sasha moving closer to him. That is until the boy said that he was hot. Mike might've choked on his popcorn had he had any in his mouth. Instead he paused and shook his head, "I didn't know that but, uh, thanks."
After talking with Sasha for a while and hearing how others treated him poorly and how he just accepted it, Mike didn't want to be mean to him. It was just a compliment anyway.