yes it is true teddy
coorect me if i am wrong but didnt the sorting hat say that Godric Gryffindor and Salazar Slytherin were the best of friends but then they had a row or something of that matter and then Slytherin departed?
so really they were best of friends at a time. So slytherins cant be all evil. its just the way people see them throught the books. most of us are cunning, sly and wise. so people do not judge by what you have heard but actually talk to a slytherin before judging