User blog comment:18emerc/How much magical blood?/@comment-1400578-20130407055628

In JK Rowling's own words (from her website):

''“The expressions ‘pure-blood’, ‘half-blood’ and ‘Muggle-born’ have been coined by people to whom these distinctions matter, and express their originators' prejudice. As far as somebody like Lucius Malfoy is concerned, for instance, a Muggle-born is as ‘bad’ as a Muggle. Therefore Harry would be considered only ‘half’ wizard, because of his mother's parents. If you think this is far-fetched, look at some of the real charts the Nazis used to show what constituted ‘Aryan’ or ‘Jewish’ blood... the Nazis used precisely the same warped logic as the Death Eaters. A single Jewish grandparent 'polluted' the blood, according to their propaganda.”''

Look up "" (and some of the related articles) on Wikipedia to see how far these sorts of prejudices can go. For example, members of the SS were required to prove they had no direct Jewish ancestors for as far back as 1750.