I am also not a downvoter (I generally try not to) but I think it's likely due to the hostile, aggressive tone, and the lack of implied values, as NancyLebovitz touched on.
I also might suggest that Rowling probably didn't mean that, since it was said by, ya know, Voldemort. Some may have downvoted because it implied Rowling agreed with it.
Here's the new thread for posting quotes, with the usual rules: