Draco's eyes canted to Snape, but he stayed silent as Nott started... was he accusing him, or stepping up as if Snape was about to attack Goyle? Either way, it was... pathetic, really, and something in Draco tugged a bit, seeing Nott that way here, where he thought he'd be better.
Wasn't that why he'd agreed to help with this in the first place? If Nott was going to get worse, he might as well be in Mungo's.