You're throwing thousands of people together as a single unit. The Dunmer are 'people' just like everyone else, they have criminals, law enforcers, cultures and opposing cultures. Just because one Dark Elf says she doesn't like necromancy doesn't mean she speaks for everyone. If you haven't noticed, there is almost always an NPC that gives you a quest or helps you kill almost every necromancer in Morrowind.
It's not one Dark Elf, that says they don't like Necromancy, the entire race is vehemently anti-necromancy. Their laws, & their two largest religions strictly forbid it, & yes there are Dunmer that offer necromancer killing quests, because they see necromancy as a scourge. That's part of the problem, because every Dunmer has an apparently inherent necromantic ability, that a great deal use with wild abandon.
And moreover, literally every family crypt in Morrowind is guarded by ghosts, skeletons, & bonewalkers. According to lore, these undead are deceased family members bound to their graves, & forced to watch over them. And yes some at least are forced, because it's mentioned somewhere, that Dunmer families have been known to tie particularly unfaithful family members to a grave site, as an ironic punishment of sorts. Hell, in one book it even makes mention of the fact that the Ancestor Ghosts Dunmer can manifest hate being summoned, because the living world is confusing, & possibly even painful to spirits.
So not only are Dunmer hypocrites, necromancers who say every kind of necromancy, except for the on they parts is evil.
They don't care, because even the spirits they practice on tell them that what they're doing is painful, & sort of evil.
Yet they do it anyway, while insisting that it's wrong, but only when OTHER PEOPLE do it.
I will concede that I am generalizing to a degree, but you can't talk about an entire culture without generalizing a little bit.
But my point is, yes. Dunmer hate necromancy. but they're also a culture built on necromancy.
Their laws, religions, & social mores all forbid it as one of the worst sins you can commit, however nearly every single Dunmer could be said to dabble in necromancy, & ninety percent of the Dark Elf families out there have a history built on necromancy, & are culturally reliant on it.
Dunmeri culture, is built upon hypocrisy.