Let's answer a question, 

How do you know the difference between good and bad?  

In time, the truth will out.  

And you will witness in the actions and deeds of people their true colors.  

Actions, as they say, speak louder than words.  

It can get confusing, especially when the bad will blame and call the good bad, and present themselves as good. 

"Woe to those who call bad good, and good bad;

Who substitute darkness for light and light for darkness;

Who substitute bitter for sweet and sweet for bitter!"

                          - Isaiah 5:20

Ask, if the same things were to happen to me, how would I feel?  

“In everything, therefore, treat people the same way you want them to treat you, for this is the Law and the Prophets."

             - Matthew 7:12

And look to your conscience and Holy Spirit to guide.

"They show the work of the Law written in their hearts, their conscience bearing witness and their thoughts alternately accusing or else defending them."

                    - Romans 2:15

You may not be able to feel the negative energy or unholiness in others, but you can feel it in yourself.  

When you lie, harm and sin, you become a liar, an abuser, a sinner; and you can feel the bad and negative changes within yourself.  

To measure how bad or unholy, ask how badly you would not like the same things to happen to you in harm.  

https://bible.knowing-jesus.com/topics/Conscience