Pure bloods and the sacred twenty eight had completely fucked with his head, some rules he still held true but her blood meaning less than his when she could best anyone in their year - apart from maybe Theo, It was ludicrous.  If Draco wasn't so clever he might still believe the lies that had been battered into him since childhood. How could Voldemort's ideals of pureblood’s being superior hold any weight when Voldemort himself was a half blood and arguably one of the greatest wizards of all time? Albeit a dark wizard - he was still a skilled wizard. Dumbledore, his sworn enemy and equal in several ways, was a halfblood. 