To continue with your analogy, moral realists claim there is one true yardstick. If you deny that it doesn't mean you can't measure anything, and that all attempts are useless. For example, people could still use yardsticks if they were approximately the same length.
I'm still not catching it. There isn't one true yardstick, but there has been moral progress. I'm guessing that this is against a yardstick which sounds a bit more "objective" when you state it, such as "maximizing happiness" or "maximising human potential" or "reducing hypocrisy" or some such. But you agree that thinking that such a yardstick is a good one is still a subjective, personal value judgement that not everyone will share, and it's still only against such a judgement that there can be moral progress, no?
In this video, Julian Savulescu from the Uehiro centre for Practical Ethics argues that human beings are "Unfit for the future" - that radical technological advance, liberal democracy and human nature will combine to make the 21st century the century of global catastropes, perpetrated by terrorists and psychopaths, with tools such as engineered viruses. He goes on to argue that enhanced intelligence and a reduced urge to violence and defection in large commons problems could be achieved using science, and may be a way out for humanity.
Skip to 1:30 to avoid the tedious introduction
Genetically enhance humanity or face extinction - PART 1 from Ethics of the New Biosciences on Vimeo.
Genetically enhance humanity or face extinction - PART 2 from Ethics of the New Biosciences on Vimeo.
Well, I have already said something rather like this. Perhaps this really is a good idea, more important, even, than coding a friendly AI? AI timelines where super-smart AI doesn't get invented until 2060+ would leave enough room for human intelligence enhancement to happen and have an effect. When I collected some SIAI volunteers' opinions on this, most thought that there was a very significant chance that super-smart AI will arrive sooner than that, though.
A large portion of the video consists of pointing out the very strong scientific case that our behavior is a result of the way our brains are structured, and that this means that changes in our behavior are the result of changes in the way our brains are wired.