After Voldemort is defeated and global wizard equality is achieved, the influx of half-breeds and less-capable wizards into Hogwarts and other magical schools grows dramatically. Criticisms of this change are met with accusations of bigotry, including calls of “you are starting to sound a lot like you know who with that talk!” This process continues, with miscegenation becoming “all the rage” for the next hundred years.
By the year 2100, magical bloodlines have become so diluted that very few people can actually use magic any longer. Magical creatures find that they cannot communicate with students at school, wands begin refusing ownership, and tensions rise as “pure” students begin to unite. The fear of a return to the Dark Days is still strong, and those critics who raise concerns over the decline in quality and use of magic are called “bigots” for their anti-muggleblood views.
In more progressive circles, prominent “intellectual” wizards begin to suggest that magic doesn't even really exist - not objectively anyway. It is merely a social construct, and witchcraft and wizardry can manifest themselves in many different forms, most of which don't involve the use of magic at all. This is met with great approval by the majority of muggleborns, though there is still discontent among those who continue to actually use magic “correctly.”
Voldemort did nothing wrong.
He was weak, inefficient, and when you have access to permanent polymorphic magic, he was ugly and not even in an intimidating way.
Lord Val-U-Mart is some tiki-torch tubby self-hating half-breed.