It seems less like the war eliminated men with conservative beliefs, and more like the period of peace and prosperity that followed made people more amenable to an expanded welfare state. Also, the biggest components of that welfare state are popular among Republicans and Democrats. There was/is definitely a factor of baby boomers being a huge voting block that protects Social Security and Medicare from cuts. But the main thing that's been driving their insolvency is not expansion of benefits; it's the longer lifespans -- of course going hand in hand with increased real medical costs as a share of GDP.