How we cite our quotes: All quotations are from Harry Potter and the Chamber of Secrets.
Quote #7
PROFESSOR MCGONAGALL: Salazar Slytherin wished to be more selective about the students admitted to Hogwarts. He believed magical learning should be kept within all-magic families. In other words, pure-bloods. Unable to sway the others, he decided to leave the school. Now, according to legend Slytherin had built a hidden chamber in this castle known as the Chamber of Secrets. Though, shortly before departing, he sealed it until that time when his own true Heir returned to the school. The Heir alone would be able to open the Chamber and unleash the horror within, and by so doing purge the school of all those who in Slytherin's view, were unworthy to study magic. Muggle-borns.
This is Salazar Slytherin's whole philosophy on magical class and purity right here. Why should Hogwarts teach students who aren't pure-blood? Shouldn't magical learning be ultra exclusive? Why should the magical gene pool be deluded with Muggles?
Quote #8
DOBBY: Dobby remembers how it was before Harry Potter triumphed over He-Who-Must-Not-Be-Named. We house-elves were treated like vermin, sir. Of course, Dobby is still treated like vermin.
It's good that house-elf living conditions improved a little after Voldemort was killed. A victory for the lower classes! But, wow, Dobby's family must be really awful.
Quote #9
DRACO MALFOY: You'd never know the Weasleys were pure-bloods, the way they behave. They're an embarrassment to the wizarding world. All of them.
Draco doesn't know he's talking to Ron Weasley (disguised as his friend, Goyle) right now. But, this pretty much reflects his thinking. The Weasleys are traitors to pure-blood wizards because they choose to fraternize with Muggles and, you know, not support genocidal maniacs like Voldemort. What weirdoes.