What he is referring to is a universal moral law. Who provides a universal transcending moral law? Where do these laws come from? Are they invented? If so why not invent more? Are the discovered? Thomas Jefferson believed so when he said they were self evident. If self evident then they are there from the start and not learned.
Obviously, the Christian is told who authored the moral law and set laws in motion. This truth, is what make me objectively say someone is wrong or right. Then we are also told to obey God rather than men so God's law is higher than man's law. Of course, for the Christian this has meant persecution, beatings, imprisonment, and death.
One day you or people you love may see the results of Christian apathy.
If we say the human mind is the author of morality then you only have opinions as we see humans are very prone to rape or murder, it happens everyday. Human well being is subjective. In survival my well being is to be stronger than the other guy.