The industrial and economic developments of the Industrial Revolution brought significant social changes. Industrialization resulted in an increase in population and the phenomenon of urbanization, as a growing number of people moved to urban centres in search of employment.
It went down. Because many people died in factories and self inflicted death rates went up due to the living conditions. This was also during a time of war I believe. That left men to die and families without them to die.
Several meanings could be agvined to this. On face value, Dr. King is saying that the men who lynched Emmett Till were morally bankrupt but hid behind Christianity and rationalized their actions for murdering Emmett for allegedly flirting with a married white woman.