Isn't it pure arrogance and hubris for some witches to refer to themselves as "Hereditary" witches?

It's entirely possible for a family to practice some sort of magickal tradition, even if they don't call themselves Witches or magickians. (My father's family did some things--lots of "lucky charms" and sympathetic magick with simple tools like twine--under the name "Stuff we don't tell our pastor about.") That said, I think that perhaps one or two percent of the people who claim the title "hereditary Witch" can legitimately claim the title. I wouldn't use it myself.