James glared at Scorpius, "He may be head of the office but I don't think protecting my sister on her birthday falls under things he would be disappointed in me for." Though you couldn't tell it from his expression, he was not so sure in his statement. Since taking his position as auror, he never had to assault someone with physical force. The repercussions of a bar fight weren't clear and he had not thought that far ahead in the future.
It wasn't something he was about to admit aloud, but Scorpius did have a point. Being an auror came with it's responsibilities and assaulting another wizard would not be looked highly upon. Sure, there were plenty of instances in the past, but he was a Potter and he had a feeling his father would make an example of him.
James decided to ignore his other comments, he didn't need to give him the pleasure of hearing that there was some truth to his words. He matched his cold expression and grabbed his drink off the bar. "We're done here. Just watch yourself." Leaves the bar and joins his previous spot at the birthday table.