Popularization work does not a scholar make, nor does it count to scholarly outlook. Popularizers are not scholars per se, and if they are scholars [like Hawking with his "Brief history of time"] it is NOT because of popularizations. And the argument is not quite "ad hominem", for it goes to the root question of the guy's qualifications [and thus credibility] as a scientist. IMHO, as a scientist he is marginal at best.
On the other hand, fine tuning is not anti-evolution. It is just mind candy for those who want to believe it.
But arguing about his qualification rather than the content of what he writes is ad hominem in the strict usage of the term.