My Father is Greater than I

Why is the phrase "My Father is greater than I" in John 14:28 so controversial?
When a 4th century heretic named Arius claimed that if God the Father is greater than Jesus, then Jesus must be a creature and not God, those who denounced Arius stated as one of their counter-arguments that since Jesus was fully man and fully God during His earthly ministry, He must have been comparing just His humanity, not His divinity, to God the Father. Ever since then, generations of cults that deny Jesus' deity have repeated Arius' heresy, and generations of Christians who denounced them and Arius' heresy included many who repeated the argument that Jesus must have been comparing just His humanity to God the Father in this verse.

Are they right?
No, for three reasons. Firstly, Jesus, who was fully God and fully man during His earthly ministry, said, "My Father is greater than I," not "My Father is greater than just my humanity." Secondly, saying that someone is greater than just one side of yourself is actually a snub that implies the other person isn't greater if the other side of you is also brought into the picture. Thirdly, the context of the passage precludes Jesus all of a sudden speaking only about His humanity: "‘I am going to the Father,’ for My Father is greater than I" (John 14:28); was Jesus going to return to God the Father in heaven only in His humanity and not as God the Son?

Then was Arius right?
Of course not, but the way to stamp out a heresy isn't to go off the rails on the other side; it's to simply present what the Bible says, and the Bible has plenty to say about and show to prove Jesus' deity (e.g., The Word became Flesh, Before Abraham was I AM, I And My Father Are One, My Lord and My God, Jesus feeds 5000, Fear Not, Lazarus Come Forth, Resurrection of Jesus).

Did God the Son come into existence later than God the Father?
No, Jesus is "God" (John 1:1), and one of the attributes of God is that He is eternal, which means having no beginning and no end: "From everlasting to everlasting, You are God" (Psalm 90:2). Jesus has always been in existence, even before "the beginning" (John 1:1).

Did God the Father initiate the existence of or give rise to God the Son?
If so, God the Son wouldn't be eternal (see above), so no.

Are God the Father and God the Son two different Gods or of different substance?
No, "the LORD our God, the LORD is one!" (Deuteronomy 6:1, Mark 12:29, see the diagram in this page).

Is God the Father more holy than God the Son?
Both are holy in Their divinity, and God the Son was holy - "knew no sin" (2 Corinthians 5:21) - even in His humanity, so no; God the Father and God the Son are both perfectly holy.

Is God the Father due greater glory than God the Son?
No, they share the same "glory" (John 17:5).

Is God the Father due more honor than God the Son?
"All should honor the Son just as they honor the Father" (John 5:23).

Then in what way is God the Father "greater" than God the Son?
God the Father "sent" (John 5:30, 5:36, 5:37, 6:57, 8:16, 8:18, 8:29, 10:36, 12:44, 12:45, 12:49, 20:21) God the Son, who said as He began His earthly ministry that He had come "for the works that the Father has given Me to accomplish" (John 5:36), and then reported to the Father as He closed out His ministry, "I have accomplished the work which You have given Me" (John 17:4). So God the Father has the relationship's "greater" position from which to have "sent" God the Son into the world to save it, and then to receive report of mission "accomplished," not that it was news to Him (see Son of God).

Does God the Father being "greater" make God the Son 'lesser'?
Jesus, our divine Creator - “For by Him all things were created, those in the heavens and those upon the earth, those visible and those invisible, whether thrones or lordships or rulers or authorities. All things were created through Him and for Him” (Colossians 1:16) - who needed nothing yet gave up everything to save us from sin and hell is already great beyond our comprehension. His declaration that God the Father is "greater" doesn't diminish His own greatness; His humility enhances it.