Manchester was a product of his times, a brave man and a disgusing liberal, I find it strange, for example, that both my grandfather and his father served in WW1, my father would have been about eight years older than Manchester, how they reached different political views.
I think that the answer is that Manchesters father, though poorly paid, never suffered through the depression, he was a socal worker and from a difunctional family, but he never really felt want, he saw it and he hated it but he never felt it.
I was amazed at the paralls in our family history that he discribed in his Marine Corps book, but the difference that I noticed was my family was in the west, from 1928 to the dy he died my grandfather never practiced his profession, Engineer, my father went to College on an athletic scholarship.
The liberalism of many WWII vets is understandable (unlike current liberals). Some were dirt poor. They had never seen a dentist and only rarely a doctor. Didn't have many clothes and food was scarce. When they joined the military it was a miracle to them. Food, doctors, new clothes, jeeps to drive, many saw their first dentist. There was wealth they had never imagined. On top of that, we won the war. Government worked for that generation.
No surprise that when the became civilians they thought the Feds could solve almost any problem.