Hadding is an autistic flim-flam man, or to use Alex's phrase, a socially-awkward detail stickler. No rational person is fooled by that nonsense. The fact that this kind of sophistry is being peddled by revisionists puts the whole enterprise under a cloud of suspicion.
Notice the personal attack by Johnson on Hadding. Though I haven't read any of Hadding's work, it sounds to me like Johnson can't deal with Hadding’s reasoning - thus the ad hominems.