Children are truly more open minded and responsible at times. Actually unlike viruses, Vampires are considered living as their cells reproduce quickly when they are injured. Also, they all need to consume something to stay alive (whether it's electricity, money, or blood). They can speak languages without doubt, and they can transform to different creatures so they have a working brain.
Why people don't consider long term consequences is because they desire immediate benefit (just like what you said). But then innocent natives die, and the bumble bee species also declines! And not only the bumble bee species, approximately 20 000 other bee species are in decline due to the honey bee's unjust domination. Another long term consequence that people didn't consider in the past is Global Warming. Though they are dealing with it now by making electric cars and attempting to use reusable/recyclable materials, it's not enough yet.
It's not hard to create mob mentalities these days. Perhaps the Vampires in the media input a hypnosis technique into their posts/words/news. Countries that we know are affected by Vampires so far are: Germany, Canada, U.S., China, Europe (and maybe France). These countries ether had many conspiracies, strange sects, sighted vampires, or caused invasions and propaganda. I think these governments might have secret labs where they captured some vampires and forced them to use their powers in communicating with other species and hypnosis to attempt taking over the world. I know that there are some good vampires out there that wish to make friends with other species (including humans) and don't want to kill/harm needlessly. Though these types of vampires are surely a minority. My friend, I'm afraid that world governments are certainly part of a worldwide conspiracy.
Roofs were never safe. Even if your under them, they can relay damage to you. They break under 1 inch diametered hail, they fly away with tornado winds at 166-200 mph, they keep fire smoke inside, and they leak water at times. Still, they're better than having no roof. They just need modifications, and maybe slightly high fences that prevent people from getting the high place phenomena. Certainly being proactive has its benefits. "Better be safe than sorry", might as well set up the cinnabar trap, and a rope trap to capture any jiangshi that attempts invading your house. Invasive species are everywhere nowadays.
I don't think that demons and vampires are related, would you say that apples and oranges are related? Probably not. Just that they are both juicy fruits with peels. As for vampires and demons, they're both living supernatural beings that can communicate. Otherwise, there are no relations. Just like how some humans are at odds with one another, so are other species. Moose males fight each other to the death so they can lead the herd. Perhaps the demon wants to help you because it has some history with vampires. Also, you are the only person I know making an effort (other than that researcher acquaintance of yours), which is better than no effort. Though the experiment shows that the dagger has a bad aura, doesn't mean there's no chance that it can do good or change in the future.