Maru kind of wanted to hurt Mr Green. How dare he make Madoka sad.

Have you ever seen a kitty scowl? Maru was doing his best to do just that. Maybe he should hiss? Angry cats hissed, right?

He jumped out of her arms and onto Madoka's shoulder, he pressed his side gently against her while he glared at the alien guy. "No, she's strong. And I'll help her be stronger. Being kind isn't a weakness and isn't a vulnerability." And he would fight anyone who tried to argue with him.