Well first off... neither blood elves or nightborne are traitors to the alliance. and secondly... the nightborne aren't Junkies as of the conclusion of their story arc prior to recruitment.
I knitpick these sorts of details largely cause a certain poster has a certain inclination towards mixing up key lore details concerning elves.
AS to why neither are traitors to the alliance. Nightborne had never been interacting with or entering into any deals or association with the "Alliance" as an official entity. Nothing to betray since they never joined. The blood elves were left high and dry and condemned. The only way they were made traitors is because they survived to spite the Grand Marshall leading them. They didn't turn on the alliance or seek retribution at all until roped into the horde during the events of TBC years later. You can call the blood elves traitors if you like, Garithos did label them as such... but it's so traitorous how those 'traitors' survived when they were condemned to die