I did also look for a denial from Goertz or Stark, I couldn't find one either. They do have a book, perhaps there is more detail there.

The "they deserve to die" quote is very damaging, and quite frankly probably the kind of thing a journalist would remember, and perhaps even report. You could conversely say that Goertz or Stark should confirm this if it's true. I couldn't find any evidence of this.