[myared]

His arguments are poor. These are the two most egregious.

(1) It Costs More and Takes Longer. Yes, designing something additional takes longer; however, if he compared the time required to add responsive code to the time it would take to setup mobile detect and an alternate theme, than this point may have some more sense even though I'd still side with responsive code.

(2) Non-Responsive Designs Usually Work. No. That's why we're having the discussion. If regular designs worked, there would not be a need.

This is a problem that a lot of companies struggle with. It's fine to criticize responsive design, but bring something to the table.