I read this claim from one religious group, in their literature. It stated:
"However, we cannot be part of God's organization and, at the same time, be part of false religion... So God commands: 'Therefore get out from among them, and separate yourselves.' - 2 Cor 6:14-17.
"What does it mean to 'get out from among them'? Well, we could not be obeying that command by remaining a part of, or giving support to, a religious organization other than the one Jehovah God is using. So if any of us still belong to such a religious organization, we need to serve notice that we are withdrawing from it."
No prizes for guessing which religion that is. The clue is in the text. But I also read these claims from another religion:
In 1302 Boniface VIII declared in the bull 'Unam Sanctam' that this church has "one head, Christ and his vicar Peter and the successor of Peter... For all men, it is absolutely necessary for salvation to submit to the Roman Pontiff. This we declare, affirm and proclaim." (DS 872; D 469) Notice how the one head of the church, Christ, has to share this role with "the successor of Peter" - the Pope? And that there can be no salvation for anyone who does not submit to the Roman Pontiff? That was followed by Pope Clement VI (pope from May 7, 1342, to December 6, 1352): "No man outside obedience to the Pope of Rome can ultimately be saved. All who have raised themselves against the faith of the Roman Church, and died in final impenitence have been damned, and gone down to Hell." (Source: Pope Clement VI, "Super Quibusdam," as cited in "Apostolic Digest, Book V: The Book of Obedience") Notice the progression from not obeying the pope to being against the Roman church, to impenitence and damnation?
If that isn't blasphemy, what is? And it's no different to the claims of the first religion I mentioned, because total obedience to their tiny group of leaders is said to be necessary for salvation. There are many more that could be mentioned but it's not worth spending time on because Jesus said we just need to come to Him, for His burden is light and His yolk is easy, unlike all those blasphemous groups who put heavy burdens on their members and who have a chaffing yolk that seems to be padlocked.
"Paradise" book chapter 23 "God's Visible Organization"