One could point out that the Nazis supported the extermination of people who, by their standards, were less than human.
The Jews, the gypsies, etc.
They managed what, six to ten million? Not counting war dead?
Modern liberals have concluded, in general, that an unborn child is less than human. Since 1973 they've managed what? Thirty-five million?
I know that the liberals are behind in the 'yearly' column, but they've made up for short annual returns with an extended culture of death that continues to reap 1.2-1.3 million dead per year.
So yeah, some people can see a political party with a socialist bent that identifies sub-human humans and makes their destruction a pillar of their political identity as similar to NAZIism.
IMHO, of course.