The Slytherins at the front of the class all looked up eagerly; they loved hearing Snape taunt Harry.
He wouldn’t want to lose face in front of the gang, but he’d be terrified of provoking Harry… it would be really fun to watch Dudley’s dilemma, to taunt him, watch him, with him powerless to respond… and if any of the others tried hitting Harry, he was ready — he had his wand.
’Snape — Snape g — goaded Sirius about staying in the house — he made out Sirius was a coward = ’Sirius was much too old and clever to have allowed such feeble taunts to hurt him,’ said Dumbledore.
In fact, compared to what he usually had to endure from Snape in the way of taunts and snide remarks, he found the new approach something of an improvement, and was pleased to find that when left well alone, he was able to concoct an Invigoration Draught quite easily.
What was making Harry feel so horrified and unhappy was not being shouted at or having jars thrown at him; it was that he knew how it felt to be humiliated in the middle of a circle of onlookers, knew exactly how Snape had felt as his father had taunted him, and that judging from what he had just seen, his father had been every bit as arrogant as Snape had always told him.