Here is my written scene about Harry explaining things to Lily:
Harry: Welcome, Miss Evans. I'm terribly sorry for subjecting you to this ordeal, but your very life is at stake, and many of your loved ones too. I couldn't let Death Eaters, the Ministry, and the Order know of our little operations.
Lily: Let me go, you little creep! I will never betray my friends, and do your worst!
Harry: I'm not asking you to spill your fellow Order members's names or addresses, or to betray their plans. We know most of them anyway, for example, Frank and Alice Longbottom, Alastor Moody, Caradoc Dearborne, Dorcas Meadows, Aberforth Dumbledore, Fabian and Gildeon Prewett, Marlene McKinnon, Benji Fenwyk. Do you need me to show their addresses too? It's all in this pile.
Lily: How? What? Who are you?
Harry: We are here to help you fight Death Eaters, and all their minions in the Ministry. However, we don't want them to know, and we want to give everyone an illusion that you and your family were abducted.
Lily: Then why do you have me tied up? And why don't you contact Dumbledore directly?
Harry: We are perfectly aware of your temper, and we know you are very angry about your treatment. I need to finish my explanations before releasing you from the restraint.
Harry: First I'd like to know your opinion of Magical Britain.
Lily: I'm not going to answer anything until you release me!
Harry: Very well. But you need to agree not to attack me at the first opportunity, or until we have finished our discussion.
Lily: Good, I promise to hear you out first. Now release me!
With a swish of his hand, the binding on Lily was gone.
Harry: Again, I'd like to know your opinion of Magical Britain. Please tell me how you really feel about it. It's important.
Lily: At first, I was very excited. A whole new world to explore, new people to know, and new powers to learn. But then, You-Know-Who just appeared and started killing people, especially people like me. And he started driving the students apart, destroying past friendships...
Harry: Severus Snape.
Lily: How do you know?
Harry: We have our sources. But please continue, Miss Evans.
Lily: I want to know who you are, and how do you know all those things about me, us; and how much more you know.
Harry: You will of course learn that in due course. For now, I'm interested in hearing more of your opinions. You already know what Death Eaters are after, can you think of a Muggle world equivalent of Death Eaters?
Lily: Nazis. They are magical Nazis.
Harry: I'm very glad that you see this parallel so clearly. What do you think of the Ministry?
Lily: They are bigoted, corrupt, and incompetent. From what James or Sirius told me, it's full of Death Eater collaborators and sympathizers. That's why we all joined the Order, Dumbledore is our only hope.
Harry: I'm sorry to tell you that Dumbledore also has very little success against the Dark Lord so far. How many notable Death Eaters has your Order permanently put out of business so far?
Lily: I can't tell you.
Harry: That's ok. Because the answer is none, both the Ministry and the Order have so far only taken out some of his curse fodders and none of his key Death Eaters. Just like we know about the Order, we also know about the Dark Lord's organization.
Lily: Why do you call him the Dark Lord? Only Death Eaters call him that.
Harry: What else are we supposed to call him? "You Know Who" or "He Who Must Not Be Named"? That's downright silly! He's of course extremely powerful, a walking weapon of mass destruction, and militarily very capable. So I think it's fair to call him the Dark Lord. Of course, if you want to be derogatory towards him, we can always call him "Tom".
Lily: Tom? I like that. Better than Dark Lord anyway.
Harry: Alright, Tom it is then. For the past 7 years, Tom has been waging a terror and guerrilla war against anyone who doesn't subscribe to his ideology of blood purity. The Ministry, with its bloated bureaucracy, divided loyalties, and hopelessly outdated military strategies and tactics, have little to no success against him. Dumbledore, despite his immense personal power and wisdom, is foremost an educator, a researcher, and not a general. Dumbledore and his Order have good intentions, but are not a competent military and political organization. As the war continues, we expect your people to suffer grievous losses, and eventually to lose this war of attrition.
Lily: You make grand claims, mister. I suppose your group can do better?
Harry: Of course, the very fact we captured you so easily and obtained such detailed information about your Order should be part of the evidence of our capabilities. I know you don't like my assessment of Dumbledore, but all good medicine tastes bitter.
Lily: So you want me to abandon Dumbledore and join you?
Harry: Exactly! Now let me ask you another question, what would happen if Voldemort wins this war and takes control of Magical Britain?
Lily: He would kill all people like me, and more.
Harry: Is he going to stop at just murdering all Muggleborns? What about Muggles, in Britain and the wider world?
Lily: If he takes the war to the Muggle world, other magical countries and the ICW would step in.
Harry: Maybe, but either way, far more people will suffer and die. Have you ever considered the possibility of him getting his hands on nuclear weapons and start the WW3?
Lily: How?
Harry: Very easy, the Ministry already has the Prime Minister of UK under its control. If Tom wins the war, he will have the Ministry and the PM under his control too. In that case, Britain's nuclear arsenal is already in his hands. But he could go further and also bring the American President under his control. Do you think those MACUSA aurors could stop him?
Lily: No.
Harry: Right, when he has the US President under his mind control, he could easily launch US nuclear weapons against Soviet Union, and here is your World War 3. Billions will die, maybe up to 95% of current humanity.
Lily: No, he can't do that. Nobody is that insane!
Harry: Then you don't know Lord Voldemort. He has been insane for a very long time already, because of his rituals to achieve immortality.
Lily: No, I don't believe any of it. This is nonsense, no person can live forever!
Harry: Maybe you should call up your old friend Severus and ask him about whether his precious Dark Lord has ever boasted about achieving immortality. Or you can ask Dumbledore about his opinion. Maybe your friend Sirius could also fill in some concepts about dark magic from his family library.
Lily: How do you know any of this? I can't blindly believe it without proof.
Harry: What kind of proof do you need? We have interrogation transcripts from captured Death Eaters. We have books about dark arts, ancient rituals, and alchemy.
Lily: I'd like to see them. Also, tell me more about your organization first.
Harry: Our organization is called the "Resistance". Our goal is to bring equality, justice, and prosperity to all wizards and witches, regardless of their ancestry and blood status. We would like to begin with Magical Britain, and we would like to turn it eventually into a constitutional democracy. Here is a sample constitution that's still subject to revisions.
[Lily went over the text briefly]
Lily: You have a very lofty goal. But that means fighting against thousands years of entrenched interests. That means revolutions and wars and more deaths!
Harry: Americans fought a war against us because they didn't want to be taxed without representation. Americans fought a most devastating civil war to free the slaves. Our parents fought a total war against the Nazis. Even the often maligned French Revolution freed us from absolute monarchy. Tell me, Miss Evans, would Muggle world be a better place without the American and French and Glorious Revolutions?
Lily: No, but magical world is different.
Harry: How so? Wizards, by default, are supposed to be magnitudes more productive than Muggles. They should long be in a post scarcity society, an utopia, and yet, we can observe extreme poverty, material poverty, everywhere in magical world. Whether it's in Knockturn Alley, Rue Maudite in France, or Boerum Hill in New York, or Kamagasaki in Japan, conditions there rival the worst of Muggle slums. When inequality and injustice reach an extreme level, there will be need for struggles and revolutions.
Lily: I don't know. I wish we could all live in peace, and prosperity. I hate wars, but I hate injustices too. I don't know. I need to think about this. I need to ask my friends. Where is James? Where are my parents?
Harry: James is still resting in next room. I'm going to speak with him next. Let me accompany to your room, your parents are there. Please don't try to break out, you will fail. Consider your stay here as a form of protective custody, or witness protection program.
Lily: When can we leave?
Harry: A few more days, after our talks are concluded.