What about "I'm the adult, and you're the kid"? On the one hand, you do need to respect the child's personal living space, but on the other you have parental responsibility to ensure that 1) that space meets some established minimum quality of cleanliness and 2) the child learns enough cleaning/organizational skills to function as a member of society.
Obviously this is completely different when the child is a fully-grown adult--at that point, what they need is not a life lesson--but for a minor just beginning to learn how to be an adult, the parents must impose their will on their child to some extent for the child's own good.
Obviously this is completely different when the child is a fully-grown adult--at that point, what they need is not a life lesson--but for a minor just beginning to learn how to be an adult, the parents must impose their will on their child to some extent for the child's own good.