Lupin looked aghast. "Harry, the time for Disarming is past! These people are trying to capture and kill you! At least Stun if you aren't prepared to kill!"
"We were hundreds of feet up! Stan's not himself, and if I Stunned him and he'd fallen, he'd have died the same as if I'd used Avada Kedavra! Expelliarmus saved me from Voldemort two years ago," Harry added defiantly.
"Yes, Harry," said Lupin with painful restraint, "and a great number of Death Eaters witnessed that happening! Forgive me, but it was a very unusual move then, under imminent threat of death. Repeating it tonight in front of Death Eaters who either witnessed or heard about the first occasion was close to suicidal!"
"So you think I should have killed Stan Shunpike?" said Harry angrily.
"Of course not," said Lupin, "but the Death Eaters — frankly, most people! — would have expected you to attack back! Expelliarmus is a useful spell, Harry, but the Death Eaters seem to think it is your signature move, and I urge you not to let it become so!" Lupin was making Harry feel idiotic, and yet there was still a grain of defiance inside him.
"I won't blast people out of my way just because they're there," said Harry. "That's Voldemort's job."

(C5 – Deathly Hallows)

Lupin glared at Harry.

"That's it," he said angrily. "Come with me."

"Let go of me," yelled Harry. He felt humiliated as Lupin dragged him outside by the scruff of his collar. He took him around the side of the house and grabbed Harry by his lapels.

"Harry, you're the one who doesn't understand," Lupin said somewhat softly. "This is a war. In war people fight for the right thing. I know of the Muggle world wars. If the Muggles decided to just capture the Nazis without bloodshed do you think they would have won. In war it is kill or be killed. The Ministry is clearly not going to last for much longer now that Dumbledore is dead. Capturing the Death Eaters is not going to work. If only we had gotten Bellatrix Lestrange in the last war, Sirius would be here."

And there it was. The words that changed Harry. His eyes went from rebelliously angry to hatred and anger.

"I will not let that monster live," said Harry so fiercely steam was practically coming out of his ears. "I promise she will not go back to Azkaban."

"And regarding Shunpike," continued Remus. "He was caught bragging about being a Death Eater in a pub last year. Even if he was under the Imperius, someone saying that would not be brushed aside. He would be taken in and questioned."

Harry had not thought of that. If someone made a joke in the Muggle world about being a terrorist, surely that person would be brought in and questioned.

Suddenly things were put into even more perspective for him.

"In other words Harry," said Lupin softly. "How far would you go to protect the people who love and care for you? I myself would do anything for you, even if it condemned me. Not just because I love you like a nephew, but because we are family. Me and you are the only ones left of the Marauders. I want to survive this war and grow old seeing you with your own family and have my own too. But to do so, we can't be forgiving, despite what Dumbledore says. It is because of him no Death Eaters got the kiss at the end of the last war. He actually believed Bellatrix Lestrange could even be redeemed. Now look at them. They've all escaped Azkaban and they're out for blood."

Harry wanted to laugh, but he couldn't. "You mean to tell me Dumbledore let that bitch off the Dementor's Kiss. She very much deserved it."

Harry changed his approach to the war after that day. Even though the coming months had seen him do things dangerously differently, it had saved more people.

Not a single Weasley died during the war. Harry had killed Bellatrix at Malfoy Manor so no one died during Dobby's escape.

And best of all to Harry, Remus and Tonks survived the war and grew old.

He was glad he took his 'Uncle's' advice.

AN: JK Rowling made Harry far too soft regarding Death Eaters. She honestly tried to mould him after Dumbledore. Harry should have fought dirty like Mad-Eye Moody. Now that's a man who got results.