Satan is very busy making every effort to hinder any and all of humanity from finding the peace of a born-again experience in Christ Jesus. One of the major ways which he uses to accomplish his will is to complicate things.
The Apostle Paul told the Church of God which was at Corinth, "I fear, lest by any means, as the serpent beguiled Eve through his subtilty, so your minds should be corrupted from the simplicity that is in Christ" (2 Cor. 11:3).
As Christianity broke loose from the bondage of Roman Catholicism in the 16th century, and began to flourish, there quickly arose various sects/cults. Of course, to be ousted from the Catholic sect, as was Martin Luther, in their eyes was tantamount to you being eternally lost. Accordingly, it was not very long until most Protestants were sure that no Catholics shared in the liberty of the born-again experience. Of course Revelation 18:4 proves that assumption to be false.
Every time that syndrome is manifested, "the simplicity of Christ" is overshadowed by man's willingness to push Christ aside, and usurp the authority of the only One who has any right to judge.
Jesus said, "The Father judgeth no man, but hath committed all judgment unto the Son: that all men should honour the Son, even as they honour the Father. He that honoureth not the Son honoureth not the Father which hath sent him. Verily, verily, I say unto you, He that heareth my word, and believeth on him that sent me, hath everlasting life, and shall not come into condemnation; but is passed from death unto life" (John 5:19-24).
And of Jesus Christ, John said, "For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life. For God sent not his Son into the world to condemn the world; but that the world through him might be saved." (John 3:16-18).
How simple it is to become and remain a Christian, as Isaiah also confirmed. "And an highway shall be there, and a way, and it shall be called The way of holiness; the unclean shall not pass over it; but it shall be for those: the wayfaring men, though fools, shall not err therein" (Isa 35:8).
Paul wisely admonished us, saying, "Who art thou that judgest another man's servant? to his own master he standeth or falleth. Yea, he shall be holden up: for God is able to make him stand."
"Seeing ye have purified your souls in obeying the truth through the Spirit unto unfeigned love of the brethren, see that ye love one another with a pure heart fervently: being born again, not of corruptible seed, but of incorruptible, by the word of God, which liveth and abideth for ever" (1 Peter 1:22-23).