Factual error: Whistler uses a Heckler and Koch MP5SD3 to mow down several familiars at the vampire library archives, but the muzzle flash is impossibly large and bright for a suppressed weapon.
Factual error: During the subway tunnel fight the subway train takes over 60 seconds to pass by Blade and Quinn. If the train is traveling at 30 miles per hour then the train would have to be a half mile long, or 66 train cars at 40ft per car. A standard subway train is only 8 or 10 cars long.
Chosen answer: It would seem Deacon has gathered a lot of strength around himself, in followers of "young" vampires like himself. After he kills Gitano he just abducts all the vampire elders, showing his followers are a lot stronger than the elders are. So they probably couldn't have killed him even if they wanted to, not unless they want to unleash a war. They thought his pursuit of the vampire god was totally pointless, so they let him waste his time and were probably trying to find a way to get rid of him.
lionhead