Q is also a meta-critique of self-possessed upper middle class busy bodies who think they know best. The Q might be all powerful, but their perch doesn’t give them any perspective or moral superiority.
Being able to rub someone’s nose in the sins of their forbears doesn’t mean it’s admirable or even useful. When the shoe is on the other foot, and Q is stripped of his powers in Deja Q, we see him as weak and simpering, which shows that his moral aggrandizing is not based on an actual principled view, but on simply being more powerful (privileged?) than the people he’s critical of.
Picard sees through Q’s grandstanding, of course. Picard knows the difference between a principled view of the world, and one based on sneering superiority.