“Boy, you just can't kill people like you used to”

“You can't just go around killing people.
You're right. You can't go around killing people.”

“Just like you kill us, we will kill you.”

“So?" Bob said. "Hat up, go kill her. Problem solved."
"Bob," I said. "You can't just go around killing people."
"I know. That's why you should do it."
"No, no. I can't go around killing people, either.”

“You see how it is with us? You can't fight it any more than I can. You've tried; you've done everything you can to kill it. But you can't kill my love for you.”

“But you can't kill a demon because they're evil spirits, like a ghost.”

“Dear popular boy I know you're used to getting everything so easily/ A stranger to the concept of reciprocity
People honor boys like you in this society”

“"No!" shouted Arthur. "What's wrong with you? They're people! You can't just kill hundreds or thousands of Piper's children because the Piper might… just might… make some of them do something!"
"Can't we?" asked Dame Primus. She sounded genuinely puzzled.”

“You can be a mama's boy, be a daddy's boy, but you can't be both. So you cling to the one you think you might lose.”

“History has shown us, that you can't allow the mass extermination of people, and just sit by and watch it happen.”