This scene together with the ending of the movie are the most intense and thought-provoking ones from the movie. I am going to write down my interpretation of this fantastic scene which is truly inspiring to me when I am fighting my own demons. I am going to take bits and pieces from the interrogation scene and elaborate.

Truth, evolution, and happiness
Joker: I know the truth. There’s no going back. You changed things.
Batman tried to clean the streets and he managed to do it. In this process, while he devoted his life doing the right thing, he made himself into something more than just a man. Deep down, he still wants to get back with Rachel after Dent takes over and fights crime legally. However, is there really a way back? Sometimes, you change so much and understand life so much that it becomes impossible to view life and even enjoy life like a simple person. It’s a price to pay for anyone living a life of high ideals, ethics, and morality. Sometimes, myself, I’d like to just think the world is a nice happy place but the more I observe the actions of people, the less I trust.
The battle of Anarchy and Ethics
Joker represents total anarchy and is a man who is treating society just the way he was treated. In the film, he makes references to being abused by his father and being abandoned by his wife after the mobs treated her badly. Batman represents resilience, ethics, a code of conduct and living as per certain rules. He also represents justice at the expense of himself. When Joker says: “I don’t want to kill you. You complete me”. I see the link between Anarchy (Impersonated by Joker) and ethics (Impersonated by Batman). This is extremely powerful because the only way to deal with the chaos of the world is by having a strong grounding into ethics. The world won’t make sense. The world will beat you down and enjoy watching you down. However, we must live a life we can be proud of, and this can be totally against what others are doing. It’s this resistance to evil which allows us to grow.
Humans, sincerity, and being an outcast
Joker: Don’t talk like you’re one of them. You’re not even if you’d like to be. To them, you’re just like a freak, like me. They need you right now. When they don’t, they’ll cast you out.”
“Their moral code dropped at the first sign of trouble. It’s all a bad joke.”
In the context of the movie, Batman has given so much of himself to Gotham and everyone is now blaming him for the chaos Joker has created. It really shows that people have the tendency to forget easily what you have done for them. The interesting thing is that Joker happens to be the person who truly understands Batman well. For example, Rachel thinks that Bruce did the wrong thing by letting Dent claim he’s Batman. However, as Alfred pointed it out, it’s not about the small lives of the individuals. It’s about doing what is right even if you end up getting hated just like it happened as the Dark knight movie evolved. Who is willing to go to that extent living the right way when you end up being completely alone and misunderstood? Sometimes, I think whether it’s worth doing all that I do for people. However, it’s always about doing the right thing which is not an easy way of living.