I just don't read it that way - they certainly try to remove what they see as bad, but beyond that they do not interfere. We don't need to guess about it. Three is plenty of first person Mind stuff in The Culture where Minds communicate with one another. Its pretty clear that Culture Minds have agendas other than total control of the citizens. It is too bad Banks isn't alive to chime in, but I think if you read all the books, its hard to support your interpretation.