I will contain my facepalming...
It took some effort not to react when Lily snapped. Scorpius hadn't meant to irritate her. Hadn't he just decided he was moving past that? At least he was still looking downwards, with the pretence of being more focused on his coffee than on her. When he did put down his mug and look up at her, though, she seemed to have moved past her short burst of irritancy, at least as far as he could tell, and had moved on to stutter over a simple word. He raised an eyebrow at her, waiting without interrupting to see if she would actually say it. It was a small letdown that she didn't.
"You did not think I would befriend a blood-traitor, you mean?" he replied, having no qualms about saying the word. He was pretty sure someone at the next desk over glanced over at his use of the word, but one benefit of being a Malfoy was that everyone expected him to use language like that.
"You are right, Wood is not the sort of person that someone of my lineage should be on such friendly terms with. Most of my family does not approve, and at every turn I get people like you questioning my motives. It is tiresome having to defend myself from both sides. Can you not accept that I have done exactly the type of thing people like you want of me and have taken a step away from tradition?"
Maybe that would settle it for her once and for all. He hadn't meant to be quite so argumentative, but he was tired of people always expecting the worst of him. Not that he hadn't done a lot to encourage that type of thinking. He could have broken free at Hogwarts and then no one would be questioning the little things like friendship with blood-traitors. Instead he was stuck following tradition and no one wanted to hear him when he tried to break a rule or two.
But just perhaps he had the foolish little notion that he wanted Lily to understand him.