I didn't know this was a meme. NWN is a good label, but when I think of a "NWN band" in a negative context, I think of one of those more boring "war metal" bands, the ones with names like Abominatortank or Deth Machinez or Ejaculator A.I.D.S. Projectile. Blasphemy/Conqueror rip-off shit, you know? Seems like way too much focus on aesthetics (bullet belts, leather, weird pseudonyms, "offensive" lyrics, "primitive" riffs) and not enough on actual songwriting or originality.
I'm not discounting the style entirely: Blasphemy is one of my favorites; I might not care for Conqueror, but I can appreciate their music for being pretty well-written; Beherit is of course classic, and bands like Diocletian and Sacramentary Abolishment/Axis of Advance show that there is certainly a lot of interesting potential in the style. I'd say that there is a parallel between the "NWN band" situation and a lot of other dismissive mimetic labels. I dig Crypticus, Decrepitaph, Hooded Menace, and Claws (and the first Acid Witch album, but for different reasons; it's like a death-metal-ized version of the best of N.W.O.B.H.M.), but there's a lot of bands on Razorback that try too hard to fit into the horror movies/old school death metal mold and completely fail at doing anything interesting musically, which might be one of the reasons that people discount that label's stuff.