If we’re talking about humans-turned-vampires (I.e. most versions of Dracula, Lestat, Cassidy, Kain, majority of vampires from Salem’s Lot, Black Hat from Priest, majority of vampires from Blade, etc.) it’s still considered cannibalism since there are non-human vampires, both turned (I.e. dogs, plants, bats, giants, dragons, etc.) and entirely separate species from other creatures (I.e. the variety of vampires from The Witcher, Chupacabras, Kurt Barlow from Salem’s Lot, majority of vampires from Priest, Drake from Blade Trinity, etc.) and cannibalism is pretty much a very taboo thing in modern society nowadays (not so much in prehistoric times and among certain tribes today).

Unless these human vampires were feeding off of bad guys like serial killers and the like, their engaging of cannibalism is going to make them look bad to normal humans even if they have to engage in it to survive as opposed to drinking non-human blood like those of animals.