Disinformation still contains information. The goal is to refocus a group searching for the truth onto anything and everything but a conclusive or productive one.
Interesting as the ancient stories and origins may be - and as much as I enjoy trying to parse through them, there is limited relevance in them.
Do we believe in original sin or 'taint of blood' crimes? To be fair, I invoke the concept when it's symbolic, so I admit to playing hypocrite, there - but when it comes to the actual hard law and due process - no, we do not believe in crimes that taint your blood. You are an individual and should be judged as an individual.
So, regardless of what blood they descend from, from a legal and practical standpoint, it is all what they have done in their life.