So he got really offended and started to cry.
I took him aside, and told him that he was a big boy, and that he shouldn't be offended by his little sister, because these were just words, and words couldn't hurt him.
Then I said, "Here, I'll talk, and you'll say, 'Stop it!'"
And it worked.
I started talking, and he said, "Stop it!"
I said, "See? Just words. I'm not offended and I'm not crying. Let's try that again. Now you say something really mean to me, and I'll show you I'm not offended."
So he said, "I don't love you."
And I got really sad.