On the knowledge of good and evil

Recently I have been watching an eight-part video series entitled "The Evil Spirit" given by Fr John A Hardon, SJ (1914 - 2000). I have found the four videos in the series that I've watched so far really informative. Fr Hardon is right. There are so many erroneous ideas and acceptance of them in the world today but many people accept these ideas unwittingly.
              Many in society think that human beings have the power to decide on fundamental issues, for example, that abortion is morally okay. I recently read a blog entry supporting the argument that something is good because human beings have agreed/decided that it is good  -  I believe the author doesn't believe in God. I disagree. Human beings can come to the knowledge of good and evil, but they cannot decide that an act is either good or evil. If human beings can decide that some action is good then it stands to reason that it follows that a government or group of people can make it acceptable to mistreat some group of human beings. One of the primary examples of this today is the treatment of Uighur Muslims by the Chinese authorities. Is there any way the treatment of the Uighurs by the Chinese authorities can be justified? No, never. But this is not because we have decided it is a bad thing to treat people in such a manner. It is because we have come to know in our own conscience, not decide, that it is unacceptable to treat people in such a manner. In other words, we have made a judgement, based on what our conscience tells us, that these actions are bad/wicked. It is not that we actually have the power to objectively categorise these acts, or any other act, as being good or bad. And to make this judgement we have to consult outside of ourselves. And who should we consult? Namely, God: Father, Son and Holy Spirit. But sometimes this is done unbeknownst to ourselves. In such cases, it is done silently, in the interior of our being, in our innermost room in the depths of our heart, and we innately know that certain actions are wrong. Unfortunately, there are those whose intellects are clouded by sin and they mistakingly hold bad actions as being good ones.