The Rouge River Plant is the great Ford Motor Co. plant in Dearborn, Michigan, that at least at one time had its own steel plant. Iron ore would enter at one end and finished cars would come out the other.
So, its a comment that the Nazis had created a factory for mass murder on an industrial scale.
A big thrill for me at age 16 in the summer of ‘66 was taking a tour of the River Rouge plant when it was cranking out Mustangs!
BTW, my uncle, RIP, was transportation VP of Ford. He was the guy who came up with the idea of putting the extra car on a rack over the tractor cab that was pulling the trailer loaded with cars! Saved Ford a ton of money by adding that extra car to the load.