Damon had seen it coming, but he actually didn't try to duck away and he didn't swing back. If it would have continued, he would have given it some fight, but Enzo was one of the most important people in his life, and he deserved this.
"I KNOW," he shouted back. "I WASN'T TRYING TO HURT YOU!" He just had a really funny way of showing it, even if it was completely true. "If I had to chose between the two of us, I'd choose you every day."
He brushed himself off and kept a distance until the situation cooled off. "I wasn't trying to do anything. I don't have any magic excuse either. It's another in a long list of ways that Damon fucked up."