Snape's Reaction to Harry assuming that he is a DE spy

[vmonte]

No: HPFGUIDX 108576

Casey:
For all we know asking those questions may be part of Snapes first
class every year, much like the "foolish wand waving" speach. I
imagine he started with Harry because he was their "new celebrity".
If Harry had answered something correctly Snape might have moved on,
but Harry didn't. Thus he could knock Harry down from his celebrity
status to that of a mortal. Then Harry back talked and confirmed
Snapes worst assumptions.

As for why Snape didn't ask about Harry's background, well, if he
doesn't ask about the other children why should he ask about Harry?

vmonte responds:

If Harry was able to answer Snape's questions he would not be allowed 
to speak in his class, like Hermione. He doesn't really care if a 
student knows their stuff (the little know-it-alls) or if they don't 
(like Crabb & Goyle). What he loves is putting CERTAIN people down. 
Snape really loves "twisting the dagger" in his students. He really 
is metaphorically like a vampire, slowly sucking the life out of 
people. He doesn't just knock them down, he lets them know that they 
are neither important nor special. I'm not so sure it has anything to 
do with keeping face with Voldemort's gang. 

I knew someone at my previous job like Snape and unfortunately I had 
to deal with this person for nine years. People like this cannot 
change. You always have to walk on egg shells with people like this. 
You also have to go out of your way to acknowledge every little thing 
they do while avoiding any positive attention focused on yourself.  
It was exhausting! I'm so glad I left that job. 

vmonte