Well, I don’t know about this, but I disagree with his proposition “being Himself supremely good, would never permit the existence of anything evil among His works” If God wouldn’t permit the existence of anything evil, it simply wouldn’t happen. But he does permit it.
If evil is simply the lack of good, then why is it personified by the father of lies? I.E. Lucifer. Look at it this way. Good things can come out of my mouth. I can also say things that are completely neutral, neither good or bad (such as I prefer orange sherbet over rainbow sherbet). I can also truly make it the lack of anything by staying silent. In order for an evil thing to come out of my mouth, I have to think it and will it. The same with an evil action. You can’t shoot anyone by simply doing nothing.
I don’t know of him saying anything about this, but I also haven’t looked very hard. Though I argue he’s wrong in the first place.