Very fascinating. In a way, Haber reminds me of J. Robert Oppenheimer, the scientist who helped create the bombs dropped on Hiroshima and Nagasaki. He was very proud of himself when the test was successful, but later he was said to have regretted creating such a horrific weapon.
It is sad that Haber never really got to repent his actions to the world. But I think he would have been horrified to see Zyklon being used the way the Nazis did had he lived.