Perhaps it's just my reading, but I've always read that scene as Hagrid being quite sneering and rude. Sort of a "shut up and do it, you little coward" attitude (though those definitely aren't the words he uses). I think part of the reason that I read him as being so rude to Draco is that he's simultaneously being so *nice* to Harry and Hermione, even though all four of the kids are there to receive the same punishment for the same rule infraction. (And while they were out of bed for different reasons, all four of them were out because of Hagrid's irresponsibility in owning Norbert.)