If he was taking care of his dog, he would clean up after it wouldn't he?
You're obviously going to defend a fellow father, since you're gonna be one and all.
His dad never made him clean it up, he did it because it was on his bed, which also belongs to his father.
And actually that's not my reasoning, more so because I don't like when people take having parents for granted, I grew up in a foster home and I'd never even think about complaining about it.