A vampire is a demon. They can be killed or injured with faith magic, and their saliva is a "magical" narcotic. They gain power from human blood. They aren't creatures of Earth.
I think "demon" has different meanings within the Dresdenverse. For example Chauncy the demon isn't the same as the hunger demon the White Court has.
Their saliva is addictive, and numbs the person while being fed on. Harry was fed on, he's had the saliva in his blood. He didn't get turned into a vamp. I dont' know if they said exactly how they turned someone.
At no point did I suggest this.
Which was the topic of discussion, and what I suggested. One clue is when Harry asked if Kincaid was human and Kincaid responded "As much human as you are"......
Lots to unpack here.
1) We don't know how much wizards are pure mortal. Could be that all wizards have some level of non-human ancestry that their power derives from. Could be that they're physically (due to perfect healing), enhanced humans- and that is what Kincaid physically effectively is.
2) Faith magic isn't restricted to affecting demons. That's headcannon. Faith magic is magic that derives from the power of faith- it's not inborn like a wizard's power. That's more or less what we know about it. It's more effective against some things, it lets you do things like curse a family into a hereditary loup garou curse that in no way otherwise abridges their mortality. Don't equate "affected by faith magic" to "demonic." The KotC are effective against ghosts, demons, materials in their way, Fae, etc- all non-demon things.
3) There's nothing about magical narcotics that's inherently demonic.
4) They gain sustenance from human blood- in two instances we're aware of (the White Court feeding directly on life force); and it seems to also feed their powers in the case of the Red Court.
They're made out of people, though, which definitionally makes them creatures of earth.
We are told how Red Court are made: Infection. We aren't told the mechanism. Could be like the Red Court- you need to ingest their blood. We do know it's not the same as the Kiss (their feeding), because that doesn't impart the Hunger, the key element of the Red Court infected- who also gain superhuman physical abilities, a weakened form of the kiss, and immortality- none of which did Harry show until the Mantle (superhuman strength). So no, very much doubt Harry's carrying a latent Red Court infection.
Maggie herself, even if the infection crossed the placenta barrier, showed no Red Court traits- and once the Red Court was annihilated, her own half-vamp state, if she had one, would have been annihilated just the like Fellowship of St. Giles had their vampire halves annihilated.
Now, the smell of brimstone- that could be a side effect of the Swords, could be specific to Harry (something he'd recognize after Lasciel), could be that when angels damage things, they use fire and brimstone (and Fallen typically are destructive), so the Swords always smell a bit like that when magically cutting. Butter's Sword doesn't hurt mortals. It only hurts supernatural monsters. It hurting Harry, I believe, was telling Harry and the reader that *at the time* he was a supernatural monster, like a battleform Denarian host. Which is consistent with the argument I've raised other places- Harry's "voice" sounded just like when he went full Winter Knight in Cold Days. Harry wasn't in the driver's seat at the time- his Mantle was. And the Knights did the same thing for him they do for the Denarian hosts- gave him the opportunity to resume control. Which he took.
I agree they were trying to make a starborn, and I think Thomas was the dry run- his birth on Valentine's being a side-effect of temporal manipulation by Margaret to ensure a "targeted" birth via her skills with the Nevernever.
Equating the Jotuns with demons is . .problematic. The concept of a demon is much more Middle Eastern- the concept we have is filtered through Christianity, but it comes from a tradition of evil spirits. Jotuns were something parallel-ish. If the Vanir had lost their war, been scattered, and devoted themselves to the ruin of all the Aesir wrought, that would be a stronger parallel to demons. Jotuns were more Cyclopses or Titans.
Loki was the god of fire. Carefully harnessed with caution, a great ally. Running loose, consuming all before him. Hence associations with red hair, shapeshifting, mischief, and danger.
