Quite possibly the darkest decade of humanity. The onset of WWII really brought out the sheer brutality of human nature. Millions of unspeakable violent atrocities were committed by men who weren't even "evil".
The 1940s also marks the onset of the baby boomers, who were raised with traditional and conservative beliefs/principles.
Friend: Name which decade of the last century you'd least want to live in?
Me: The 1940s