Seems to me that the claims of other religions does come into play.
William Miller based his beliefs on the Bible. So did Roger Williams, Alexander Campbell and Charles Taze Russell, to name just three.
Moses used miracles and established his legitimacy through pillars of fire, plagues, thunder and fire. Jesus is said to have established his legitimacy through the scriptures and through miracles and witnesses. Muhammad claimed to see an angel and have revelations. Joseph Smith produced the Book of Mormon, also was said to have healed the sick, had angelic revelations. Ellen G. White was said to have had revelations and visions throughout her life and Herbert W. Armstrong also claimed inspiration and divine revelation. Thus, the followers of these religions, or sects, could be argued not to be manmade at all, but were done through the instrumentality of God.
Of course we're talking claims here.
But now comes Charles T. Russell. No revelations. No visions. No divine guidance of note. Just a Bible student.
Even though he was one of a long string of Jehovah's Witnesses, who appointed him the head of the organization? Who ordained him? How was he called to the ministry? Who was the leader of the church before Charles T? If the church existed before him, well, who was running the show?
Let's say I decided to start a religious group that had every single tenent of belief as the Witnesses do today. Let's say I believed exactly as they do. Would my church be just as legitimate as theirs? No, they would say, for Jehovah has but one church on the Earth. Fine, I reply, but where is that church and how do I know? If I lived in 1598, where would I find a Kingdom Hall? Where would I find Jehovah's organization on Earth? There is no recorded history showing that such a group ever existed. No one had those beliefs. And if they did, who was the leader? Was he self-appointed, like Charles Taze Russell, or did God choose him?
One website that advocates Russell's ministry states: "Russell saw in the scriptures and wrote about have come to pass with remarkable accuracy. Does this prove him to be an inspired prophet? By no means! No one has been inspired of God since the days of the apostles." Hmmm. Well, if no one has been inspired of God since those early days, then that means that Russell was not inspired, and as such must be considered as a blind leader of the blind. It also means that the leadership of the Watchtower Society today also must be bereft of inspiration and guidance.
So what would be the consequence of tearing up one's weekly records? Or refusing to answer the summons of the church? For the church cannot exist without inspiration and prophecy, for one man's theology is no better than another's.
That's what I mean "manmade."
If the Jehovah's Witnesses is not a manmade religion, then what is it?