Marmaduke's owner-lady is guilting him into not killing her for trying to give him a bath.

Special "Choose Your Own Level of Anthropomorphization" Edition

Marmaduke is an aggressive and enthusiastic debator, regardless of what issue is being discussed, or which point of view he is arguing against, or the fact that he cannot speak a language.

OR

Marmaduke is barking at a couple of guys for being loud.

Marmaduke is staring down a fortune teller, daring her to say something negative about the future of dog food and incur his fearsome rage.