That’s what I meant, not that it’s a monolithic rule.
Even in the most anti-Catholic sects (like the SDA) there are charitable people who do not subscribe to the anti-Catholic bigotry they are taught.
May I ask why you put protestant in quotes? If you’re a validly baptized Christian who is not Orthodox or Catholic, you are a Protestant.
All the worlds 2,300,000,000 Christians fall into one of three Categories: Catholic, Orthodox, Protestant.
Under Catholic we have canonical Roman Catholics, Eastern Catholics, and noncanonical catholic groups like Old Catholics, SSPX, etc.
Under Orthodox we have the canonical Eastern Orthodox, Oriental Orthodox, and Assyrians, along with the noncanonical breakaway orthodox groups like Russian old believers, Greek old calendarists, etc.
Under Protestant we have all other validly baptized Christians who are not Catholic/Orthodox. Methodists, Presbyterians, Evangelicals, Lutherans, Anglicans, Episcopalians, Baptists, non-denominational, Bible-only, Pentecostals, etc. These groups ALL have one thing in common - they can trace their roots back to the 16th century or more recent movements.
So if you identify as a non-denominational Christian, you are in the Protestant Christian category. Either that or non-Christian.
Nondenominational is a modern American thing, and it’s a misnomer. The only true non-denominational Church is the Catholic Church. All other churches are denominations that broke away from the Catholic Church at some point in the past.
I suppose if you wanted to you could create a fourth category: pseudo-Christians. These would be those who self profess being Christian, but whos beliefs put them outside mainstream Judeo-Christian reckoning. These groups could include Christadelphians, Jehovas Witnesses, Mormons, Salvation Army, Seventh Day Adventists, etc. You could probably lump certain non-denoms in with this category.
Personally, if I was non-denom, I’d much rather be classed together with other Protestant Christians than with the pseudo-Christians.