> If I choose to believe Banks' quote, then I have to interpret The Culture as merely the best possible society, in a universe where human nature severely constrains what societies are possible.

I'm not sure why you wouldn't just take what Banks says at face value. Living in the Culture would for the majority of people on on Earth be far preferable.

But I do think you're close to correct about what Banks was saying on the darker side of the message. Every book of his that I've read (including the non Culture novels) has a darker side. It always seems to be about the inevitably of conflict in the presence of the human condition. And the terrible cruelty this can result in.

Nevertheless, try as I might, it confounds me how anyone could look around at the state of life on Earth today and think "yeah, much better than the dystopia of The Culture".