I was raised Lutheran, and I know our church did not consider Unitarians, Quakers, Mormons, Jehovah's Witnesses, 7th Day Adventists, Christian Scientists, Moravians, the Amish, or Mennonites to be protestants. They viewed each of these to be religions that departed from scriptural teachings in order to add new things to the religion. They also taught that Catholicism was a perversion. This division among Christian religions will be impossible to overcome. Lutheranism taught that because Luther was the first to depart from Catholicism that his rebuttal was proper and all other interpretations were wrong. I think you'll find that many other religious organizations teach similar ideas.