Why is it people always assume that all Slytherins are evil? Look at Regulus Black. Look at Narcissa Malfoy. Look at Severus Snape. Look at Horace Slughorn. They weren't evil.
Why is it people always assume that all Ravenclaws are geniuses? Look at Gilderoy Lockhart. Look at Quirinus Quirrell.
Look at Sybill Trewlany. Look at Luna Lovegood. They weren't geniuses. (Although I do think Luna was smart just not a genius).
Why is it people always assume that all Hufflepuffs are useless idiots? Look at Nymphadora Tonks.
Look at Cedric Diggory. Look at Hannah Abbot. Look at Ernie Macmillan. They weren't useless idiots.
Why is it people always assume that all Gryffindors are the definition of awesome? Look at Peter Pettigrew. Look at Romilda Vane. Look at Lavendar Brown. Look at Cormac Mclaggen. They weren't awesome.