1. Go to the root of the problem. Why is the person behaving irrationally or going out of their way to do something which would seem like a colossal waste of time and resources to an objective onlooker?
2. What is the messed-up logic prompting them to rationalize their increasingly harmful actions and words?
3. Why is there a Messiah complex or a refusal to see truth for what it is?
4. What is the person's agenda?
Once you realize where their actions are coming from, you can combat, otherwise you will be stuck helpless and lost forever.