Sometimes, a character just can't bring themselves to Kick the Dog. Maybe their target is a Friend to All Living Things, painfully cute, comically Wrong Genre Savvy to the point of being pathetic, or so obviously helpless that even a Card-Carrying Villain has a pang of conscience over attacking them.
So they look for something about the target to get mad about.
This can be shown as either something the dog-kicker is saying or doing beforehand while actively looking for an excuse, or after the fact, as part of the internal monologue of an Unreliable Narrator or a justification given to someone else. In most cases, the excuse is a flimsy one; the person wants to kick the dog for reasons unrelated to the dog itself, but feels bad about targeting someone undeserving of being kicked.
Can be a subversion of a Pet the Dog moment, by setting things up to show that they aren't without decency - but then they undo that by finding the excuse and kicking the dog anyway.
Conversely, the would-be dog-kicker might be a nice person, but have reasons to think they should want to Kick the Dog, or at least act like they did. The Dog-Kicking Excuse tries to assuage their guilt at doing something to the dog that they know the dog doesn't deserve... or more dramatically, which they deserve because of their past actions, but which have been overshadowed either by atoning for their sins, or because they have won their dog-kicker's heart.
Compare Give Me a Reason, where the character wants to lash out so badly that he goads and provokes the target into providing the excuse.
- In one of Aesop's Fables, a wolf comes upon a lamb and wants to eat it, but is struck by its innocence and feels he has to have an excuse for the killing. He therefore shoots off a number of accusations, which the lamb disproves one by one. The wolf then decides it doesn't matter if he doesn't have an excuse. In the Russian adaptation by Ivan Krylov, the wolf finally comes up with the now memetic "It's your fault that I'm hungry!".
- Lee Ann Womack's song "I'll Think of a Reason Later" is about a woman wishing she had a more justified reason to hate her romantic rival and excuse her "childish" spite antics like drawing a mustache and horns on a photo of her.
- Carla Ulbrich's "Please Do Something Stupid" is about a woman trying to find a reason not to date 'the perfect man' at a time when she is trying to focus on other parts of her life.
- Whateley Universe: Madcap, a ditzy wannabe supervillain whose main power seems to be re-activating power items that had lost their mojo, raided a convention of superhero/supervillain fans which had a large selection of such items on display. Needless to say, several ex-villains figured out that she would be drawn to something like this, and arranged for their old toys to be on the roster, with the plan that they could get them back. One of these, Plunderlord, was so exasperated with Madcap's incompetence that he couldn't bring himself to rob her, so he prodded her into saying "something stupid or obnoxious" so he could feel better about it. Unsurprisingly, she obliges, and he takes it.
- Halloween Is Grinch Night: Grandpa Josiah says that the noise of the animals disturbed by the Sweet-Sour Wind riles up the Grinch, but given that the Grinch is actually disappointed when the wind dissipates, it seems likelier that terrorizing Whoville is just something he likes to do and he uses the noise as an excuse.