Then what conditions were present in the 1950's that prevented school and work place shootings?
1. People were more responsible citizens back then.
2. Society was more homogenized back then.
3. Survival was more difficult back then, because people didn't have a giant, intrusive nanny-state to take care of every real or perceived need.
Item #3 is particularly important, for I believe it is an underlying factor in many of the social pathologies we see on a regular basis in this country. We are so affluent as a nation that we are literally bored to tears.