Apparently the Annoyed Librarian continues to live up to the name. I learn this second-hand by reading a post by Laura at Llyfrgellydd, and watching a great vlog post by David Rothman at davidrothman.net. David, I too encourage you to communicate via this medium in the future - really enjoyed that!
I looked up ad hominem for my own edification - the Apple dictionary defines it thusly:
(of an argument or reaction) arising from or appealing to the emotions and not reason or logic.
• attacking an opponent’s motives or character rather than the policy or position they maintain : vicious ad hominem attacks.