I feel like there is a breed (most?) of designers that think that design is the final gift from God. The problem is that they seem to not realize that software design happens beyond a pretty UI. Or even a well structured design spec and a good UI to display that. They don't seem to get that what is under the hood involves a lot of design skills. Design isn't making stuff look good and feel good to use. That is a specific subset of design (UX design, UI design, etc.). Design is a creative and decision making process. Design under the hood is of paramount importance. Software designers, architects etc are always making design decisions. Unfortunately a lot of developers don't feel or think that they are actually designers.
So this jackass in the end is correct, design is king. But he unfortunately does not know what design actually is.
Never call a man a fool. Borrow from him.