Well, first of all, I am not sure what version of D&D you played or maybe it was your DM who allowed good undead, but typically that was not the case. If we are going to use D&D as a guide, then check out my favorite AD&D Module Series "Ravenloft". I am also not sure what "lack of knowledge" you are talking about; we are talking about things that are not real and there are a ton of stories of undead with different origins. My opinion of vampires comes from Bram Stoker's Dracula. Not sure it gets any more "authentic" than that.
Regardless, this is my opinion. I did not name call or try and make anyone feel bad for their choices. IMO, vampires should be evil. No exceptions. Of course, if you disagree, that's totally fine. I was just voicing my frustration because I love this AVN and was really happy with it until this latest revelation. So, for me, it's just another twist on Twilight, and let's all be honest, Twilight was hugely popular and it did start a trend; I never said it started the whole good undead thing.