Setting aside the usual arguments on the anti- and pro-AI art debate and the nature of creativity itself, perhaps the negative reaction that the Redditor encountered is part of a sea change in opinion among many people that think corporate AI platforms are exploitive and extractive in nature because their datasets rely on copyrighted material without the original artists’ permission. And that’s without getting into AI’s negative drag on the environment.
I disagree with the other poster, I’d say your child is an artist making maybe the purest form of art in the world, taking their life experience and putting it to paper. I’d dare to say that letting them type out a random prompt and getting a decent image out of their limited vocabulary would be much less impactful than the most crude stick figure drawing of the two of you together.