Luke would've retaliated with something sarcastic about his underwear, but Mao was already back on the bed before Luke could make any such comment. Months of fighting with Mao had told him that the other boy wasn't in one of those angry, pissy moods - the kind that meant that he was actually dangerous. Even so, Luke automatically generated a full-body field around himself, just in case. After what had happened last time, Luke wasn't going to take any more chances at being the victim of a flying ninja kick.
"Ew! Keep your socks to yourself you jerkwad," Luke returned, deflecting the sock from his face with a more pointed force blast. Actually, it was kind of nice to use his powers like this. It was good practice. Ordinarily, Luke didn't get to practice much except when he was in his room with the door closed, and even then his parents could walk in on him at any moment.
To be perfectly honest, fighting with Mao was the best thing he could do as far as training went - it made him think fast on his feet and it forced him to aim well and keep the strength of his fields in check. If things hadn't been so weird between them, Luke might've suggested that they wrestle or something a little more regularly (and on friendly terms). Not now, though. Not until Luke was sure that Mao was over him.