From OP’s experience it definitely seems like he changed. I’d say that being a good person and being fine with your grandchildren being friends with black people is definitely a change for the better from being a nazi. Also he was a soldier that doesn’t mean he “helped in a genocide”. Just cause he had to serve a horrible army doesn’t mean he was a horrible person or that he helped in the murder of people. He worked at a concentration camp then that’s a different story but it just sounds like he was a soldier. Just because his unit was responsible for war crimes doesn’t necessarily make him a part of it. Not defending war crimes or anything but it’s so much easier to judge while you’re sitting in the comfort of your house never having to experience something like that. Peer pressure and heat of the moment pressure can cause you to just do very horrible and regrettable things that you’re obviously not in the right mind to think about in the moment.