The point of Magneto is that he does all these horrible things and will never stop because he can't shake his fear of something like the Holocaust happening again, and because we know what the Holocaust is as a real event we understand that better than if it was some fictional Marvel thing. Changing it would completely defang the character, remove critical historical and thematic texture from the franchise, and make me cry like an 8 year-old. Wah, wah, wah. Even if it's not referenced, it drives everything the character does. And it's been referenced in every major story he's been in for the past few years like IvX, Secret Empire, The solo series, Blue, and Black.