JKSManga
I understand Oscar's fear but I would definitely bet that if Quinn turned around a said he's on the way to become king of the Vampire so will have full control over all of them Oscar will be a lot less worried. Plus it's awesome seeing Owen take Quinns side immediately like "ow so your a Vampire, ok, I'll still be on your side though".
And so its finally being revealed! And Oscar of course is keeping his doubts about Quinn. Though, you can't blame him. It's not necessarily Quinn hes concerned about, it's other Vampires. And honestly he has good reason given that even in the past, some vampires protected humans, while others wanted to rule. There are still those out there that want to rule. In this case he needs Quinn even more, since Quinn wants to protect humans, and isn't loyal to Bryce either. Though he still has some allegance to vampires themselves (the 10th family). On a side note, wonder how the 10th is doing back on the planet.
Parasites and other microorganisms feed off of humans. Humans fear vampire because the vampires are higher up in the food chain. Quinn and Sam are more mature beyond their peers, they still have aspects of an 18 year mentality. Richard is the one who can talk with confidence and cracks a joke to lighten the already sour disposition of the older crowd.