How to deal with sadistic people in your life?

Sometimes in life, you are dealing with stupid and vicious people. People who find pleasure when other people are disturbed or not happy. People who are more interested in other's suffering more than their own happiness. It can be very tiring and excrusiating experience for you, if you are not a thick skinned person. The more sensitive you are, the more you suffer in such situations.

The question is, how would you deal with such people?

The first situation is when they are not directly affecting you

The simple answer to this situation is, you do not need to deal with them, unless you are their guru or someone who is on a mission to save the world.  

They are already suffering from a disease of not being able to prioritize their own life. Nearly their whole existence is busy in living and observing someone else's life. They are already losing their life in such a fruitless pursuit and you don't want to add into their life's difficulties. If it does not concern you much, then ignore them and move on. Let them do what they are doing. 

Do not also even try to advise them about their problematic ways of life and how their energies can be used somewhere much better place. They will misunderstand you. They will think that they are getting to you. 

Instead, let them deal with their life and move on. You definitely have much better things to do in life instead of dealing with some obviously mentally challenged person. 

The second situation is when you are directly dealing with such people

The first and most important thing to do is, not to let them know that they are getting to you. That is the oxygen of their existence. Without that their purpose of life is lost. Use all your intellect to create a scenario where they start feeling that they do not matter that much to you. You are not even registering what they are doing or trying to do. Take their dirty pleasure away by making them irrelavant for you. This should most of the time take their attention away from you. 

They would move on to the next reactive person who can get them their pleasure. Now, it is upto that next reactive person to learn something which you have just learned, making such sadistic people irrelavant and thus powerless.  

Most of the times, such people won't do something completely obvious or illegal which can be noticed by everyone and can be proved with ensuing repurcussions. 

But if they do, do not ever be scared to take one of the very difficult decisions. 

Either completely forgive them or teach them the biggest lesson of their lives so that their whole thinking process and personality changes. Nothing in between would serve you or them better.