Can you just imagine how frustrated and angry Snape is? Not only was he just insulted by his childhood bullies in front of a student, that student is ring leader’s son. And just when he’s all ready to take it out on Harry, Remus comes along and talks him out of trouble, just like he’s I’m sure he’s done a number of times in school. And he can’t do anything about it.
Snape obviously knows, and Remus knows that he knows. I find it very impressive that he is able to successfully navigate this situation by using the fact that Snape can’t out him without explaining the true extent of the friendship between Remus, Sirius and James. Which everyone seems to think its best that Harry does’t know. So Snape probably isn’t allowed to tell, just like he isn’t allowed to tell that Remus is a werewolf.
Poor Oliver, no one get’s it, do they? Do worry I understand you. You can’t cancel Quidditch!