In my readings of ancestral traditions of witchcraft, it is always thought that people who have the spark of witchcraft in them are the ones drawn to it. Its not like people go about saying, oh you want to do witchcraft? well you can’t because you weren’t born with it. Instead, they explain the draw and commitment to witchcraft by some sort of psychic inheritance and certainly not one limited to a particular race of human beings. When I have spoken directly with people who use the red-thread language, they confirm my understanding of it. I am sure there are some a-holes out there that are very exclusionary about it, but the vast majority of people that believe witchcraft is inborn do not mean it to exclude people interested in the craft, but to include them and explain their calling to it.
For many people finding witchcraft is like coming home. Which isn’t to say it will be easy for them, there is often a lot of complexes and such to work through, but the drive, the draw, the call is explained in the lore of a number of traditions as given by spirits or awakened from an inherited spark. Explanations include fallen angels, fairies, or primordials giving science and magic to humans, Atlantis, a shooting stars, Lilith and Cain, Tubal Cain and Namheah, Small dark people, all witchcraft comes from Africa (and science says all humans are descended from Africa, so that’s very inclusionary), Aradia and Diana, and so on.
Then from there the craft is passed on through either secret teachings, reincarnation, through inherited traits that can be awakened, and so on. I do personally believe once a witch always a witch, in reference to reincarnation, but that doesn’t mean you couldn’t start that string and be the first and future incarnations may continue. I just don’t have an investment in proving or disproving who is a witch. And I am suspicious of people who do get all arrogant about it. If you have to prove other people aren’t witches to prove you are, then what are you even doing? Witchcraft is not about that.