And that logic isn't really sound, as I see it.
Pale Masters are, in effect, necromancers. They twist and enslave the souls of the departed, keeping them from their final rest and quite possibly also desecrate their mortal remains. Yes I know the summon function doesn't really indicate it but necromancy generally requires earthly remains to work with or the summoning of a departed soul. Not to mention that the ritual for creating a Dracolich is, as I remember it, is considering unspeakably Evil (capital-E, not the morally relativistic evil).
So however you cut it Necromancers are being nasty to the mortal remains of somebody's loved ones (and no, assuming that the remains you are defiling belongs to an evil person doesn't really make a difference) whereas Fiendlocks at least only summon Evil beings from another plane to serve them, and Feylocks just serve an odd and capricious patron.
Honestly I don't see how Pale Master can possibly get away with being Neutral alignment if necromancy is considered Evil. And from a mechanical standpoint it just seems a very convenient meta-gamey option too