I fear that this argument is too sci-fi to be taken seriously by the overly literal personalities that tend to dominate HN, so let's make it clear: he's not actually saying that "robot scientists" are going to take over. Brain is performing a reductio ad absurdum -- he's taking the other side's argument to the extreme to demonstrate the fundamental logical fallacies involved.

We don't need to wait for robot scientists to see the consequences of automation -- it's happening right now. Smaller numbers of skilled laborers are replacing larger numbers of unskilled laborers. To make the argumentative leap that this is a sustainable process, you have to prove that somehow, we will dramatically reduce the number of people who depend on unskilled labor to to make a living. I have yet to see a convincing proof that this is occurring. At best, we seem to keep shifting the kind of unskilled labor that we need, and paying less for it.