the original comment was genuine confusion, and totally understandable, the later argumentative bloke is just being that - he obviously knows what Northern Soul is, and has a grudge against it for some reason. i'm guessing he's British because of bits like mentioning 'scrubbers from Stoke' and so on.
he's just someone who doesn't (and won't ever) understand the importance of all stages in the chain of any soul and dance music - from the songwriting and performance, the arrangement, production, to radio deejays (at the time) and record collectors, club deejays and dancers in the period since.
it's his 'rockist' attitude - that artists are somehow separate and above everyone else involved - that is unlikely to change. while it's ultimately the performance which gives records that 'certain something', they seem to forget about the songwriting, the arrangement, the studio band, the producer, and so on. and the records were meant for nightclub and radio play in many cases, so that had a huge effect on the sound and development of the music, and once you realise all that, then extending it to see that the championing of rare or forgotten sounds in the period since is important too is quite an easy step to make.
edit - that's a long post, but i've seen this attitude a lot in various places and various forms, and while it seems a bit irrelevant, that's ultimately what it boils down to. i can maybe see his point on this clip, since it's a famous track, and not really associated with Northern Soul, but certainly not worth arguing about, and that's his strange grudge coming out