I think the argument is that they were prison/labour camps and once famine struck by the end of the war you had mass death from starvation rather than industrial murder. Then it gets used as a zionist political tool.

Not saying I believe it for a second but that's the gist of the argument as I've understood from lurking on /pol/. Either way it's a disgrace and I don't think mass political movements are above active participation in genocide, Khmer Rouge being another example. Honestly this type of discussion makes me uncomfortable but it's good to know how people who disagree with you rationalise things.