Franc has this asinine video posted on his blog:
Now, our standards of living are undoubtedly always going to improve over time. This is because as time goes on, we develop new ideas, new technology, and better ways of doing things. So sure, standards of living probably increased during slavery. Similarly, our standards of living have been increasing under the horrific statism that Chomsky supports.
So Chomsky is right that rising standards of living didn't justify slavery. What he fails to understand is that free-market capitalism (to the degree that it exists) directly causes and encourages our present level of innovation in a way that no other economic system ever possibly could. It's not merely incidental or correlational. When people are forced into cut-throat competition to please consumers and constantly improve/invent better and cheaper products, it inevitably raises our standards of living. The people who have benefitted the most from this are the poor, who have access to things that would have been unthinkable for the historical elite.
The pampered anarcho-socialist on YouTube typically sits in a big, comfy room with a high-quality lap-top, web cam, head phones, decent clothing, and a fridge nearby--telling us how vicious capitalism is. How hard life must be for them!