I gotta say, I’m pretty impressed with Harry’s perception here!
I mean think about it, Harry really doesn’t know the details of Voldemort’s regime at this point. What does Harry know about Voldemort’s regime at this point?
Voldemort was a ‘dark’ wizard and gaining power and followers
Voldemort killed a lot of people, including his parents, and tried to kill him
People were terrified to the point that they still won’t say his name
Dumbledore’s the only one Voldemort was ever afraid of
Voldemort hadn’t tried to take over the school when he was at the height of his power yet
But he doesn’t know the details of Voldemort’s prejudices, ideals, backstory, or motivations. Knowing that this is exactly what is beginning to happen in book 7--they were teaching dark arts at Hogwarts and Voldemort announced that Slytherin would be the only house to stay--I am impressed that Harry gathers the size of the issues he’s dealing with.