The point isn't that other lore allows elven vampires, it is that we don't. Pointing out that other lore allows it means nothing at all.
As far as half-humans, they can not be infected. Once 'bitten', their other half overrides the disease.
I'm gonna go all Devil's Advocate on this, because I still feel the answer should be no, but:
Pointing out that other lores allow it actually does mean 'something', that being that it can work and can be enjoyable when done correctly. What you've said is kinda like saying,
"Hey, I realize the rest of the world is using the metric system, but we
don't. So pointing out that they do very well with it means nothing to your suggestion of using it."
Similarly (and much more arguably) "I realize many cities have little to no gun control, but we
do. So pointing out that those cities have significantly less gun crime and violence than we do is completely meaningless to your suggestion of removing it."
Now, having the opinion that just because they do well with it doesn't mean we will, or that we even should, is perfectly acceptable. But saying that fact is meaningless is rather wrong. Especially since the fact given actually is the entire meaning behind the suggestion.
Because other countries successfully use metric, perhaps we should?
Because other cities fare better without gun control, perhaps we shouldn't.
Because other lores still enjoy vampires of other races, maybe ours should too.
It's just that the meaningful reasons
not to add them outweigh the reasons
to add them.