His reply is a bit vague, but as I recall this has actually been studied and it turns out that (for instance) other animals have blood coagulation systems that are lacking several of the 30 supposedly essential parts and still work fine - see e.g. http://creationwiki.org/Blood_clotting_is_irreducibly_comple... and the usual anti-creationism resources. Similarly, the supposedly "irreducably complex" bacterial motors turn out to be made of components that originally evolved for other purposes and were repurposed.
I agree that I was vague, however my response was not intended to be an absolute refutation of every argument that follows that pattern, otherwise I'd be playing whack-a-mole with arguments forever. It was meant to be a general explanation of how the argument makes a large assumption that would be pretty easy to refute with further research. As the person above did with a link.
Also, I did give further reading with the selfish gene for a specific example of a bacteria's flagellum.
