Yeah but a lot of opressed people identify with slytherin, actually most of the slytherins I know are opressed in some way, so I get the point of view you've reblogged but I also get that it can be very disappointing for someone to see that even in a fandom every one shit on them. I mean, fandom and especially harry potter are (or are supposed to be) safe places, where you go to forget and feel better, so I think the people talking about slytherin are the same people who are oppressed (mostly)
Most of them are purebloods and many are death eater-friendly, which are largely considered to be a metaphor for Nazis (and Voldemort for hitler—and the whole war in Harry Potter for WWII). Many Slytherins, like the Malphoys, are part of the elite. Pure bloods are a metaphor for whiteness/aryan-ness—or at the very least, a privileged class. JK Rowling herself talk about drawing from Nazis/Hitler in creating the dark side of Harry Potter http://theroguefeminist.tumblr.com/post/86853776223/theroguefeminist-lipstickmisandry
Now im not saying slytherins are wholly synonymous with death eaters, nor am I saying that defending Slytherin is the same as defending Nazis, but imagine one branch of your school has a high volume of neo-nazis and white supremacists in it. Sure, not all of them are neo nazis and white supremacists, but as they say, a little shit in your shake is still shit in your shake. It would be enough to be wary of that group. The pure blood bigots in Harry Potter are an equivalent/metaphor for antisemitism/racism and and/or other forms of bigotry. I’m not trying to say Slytherins are all bad, but if Pure Bloods are the privileged elite, Slytherin is the house where they flock to and are treated best. And people are quick to forget Salazar Slytherin, the founder of the house, was a pure blood fanatic and was all tied up with the dark arts and put a fucking giant snake under a school full of children. His philosophy on who should be taught was, We’ll teach just those whose ancestry’s purest. Translated in terms of race/ethnicity, it’s outright bigoted.
So it’s not exactly like the house of Slytherin didn’t earn its terrible reputation, anyway. But either way, I don’t see how Slytherin is at all a metaphor for the oppressed. The only parallel would be Slytherin is demonized. But Slytherin is demonized because it's tied to the wizarding world’s equivalent of white supremacy. So…