Crimes against humanity are usually categorized as war crimes that targeted civilians or genocide. They can happen in a time of war or peace, and are when there is a wholesale policy of dehumanizing a certain group of people and taking action against that group. The title for the crime is because we believe, as a human race, that when one part of us suffers in this manner, it is an attack and a crime against us all.
While Paul did not have in mind the International Criminal Court, he did detail a crime against humanity:
They don’t please God, and they are hostile to the entire human race 16 when they try to stop us from speaking to the Gentiles so they can be saved.
Paul was speaking here about the non-believing Jewish people in Judea who were opposed to the Gospel. By attacking the prophets, killing Jesus, and seeking to prevent the spread of the Gospel to Jews as well as Gentiles, they were hostile to the entire human race. This is because only the Christian Gospel message can truly bring healing and wholeness to the brokenness of the world and in each one of us.
In this line of reasoning, anyone who impedes the spread of the Christian message is an enemy of humanity and has committed a crime against humanity. This is not to say that those who oppose the spread of the Christian faith would ever be brought up on charges at the Hague. Our society has decided that it can do well without any one religion being promoted. Ironically, that is a crime against humanity as well, from this biblical point of view.
Do not be complicit in this crime. Do not be a co-conspirator with those who seek to keep the Christian message marginalized. Share your faith and the reason for the hope in you with others around you. Some may think you are weird or strange. Others may think you are judgmental and self-righteous. Yet those uninformed slanders are nothing compared to the charge of being an enemy of the entire human race. Do not commit a crime against humanity. Tell people about Jesus.