"Here is a clear statement by Paul of the deity of Christ."
If Paul had wanted to make a clear statement equating Jesus with God, he sure did it in a funny way - a series of verses that are highly contentious, whether between trinitarians and unitarians or just between trinitarians themselves.
IMO something clear would have been something that included "Jesus is God." Easy! Because this is an earth-shattering claim for Paul, an observant Jew who believes God is Spirit, you would think he would not only state it once in one letter, but repeat it loudly and clearly. Instead, he uses a word here which can mean all sorts of things ('morphe'), in particular 'shape' or 'outward appearance'.
Strong's Greek 3444: Form, shape, outward appearance. Perhaps from the
base of meros; shape; figuratively, nature.
On the other hand, St. Paul distinguishes time and again between Jesus and God. So which is the proper hermeneutic - a cryptic, highly debated sentence which suggests to some that Jesus is God, or clear, repeated statements distinguishing them? My hermeneutic favours the latter.
Philippians 2 5-11:
"Have this mindset in you that was also in Christ Jesus, who, though
he was in the form of God, considered being equal with God not
something to be grasped, but emptied himself, taking the form of a
servant, being born in the likeness of men; and being found in fashion
as a man, he humbled himself, becoming obedient to death—even death on
a cross! And therefore God raised him to the highest place of honor
and gave him the name that is above every name, in order that at the
name of Jesus every knee will bow—in heaven and on earth and under the
earth — and every tongue will confess that Jesus Christ is Lord, to
the glory of God the Father." (Revised English Translation)
(As a sidenote, the passage distinguishes between God and Jesus just after 2:6-8 at 2:9. "And therefore God raised him to the highest place of honor [...]")
The article you linked to explains fairly clearly in what sense Jesus was 'existing' as the 'morphe' (form) of God and instead took on the 'morphe' (form) of a servant:
"Scripture says Christ was the “image of God” (2 Cor. 4:4), and Jesus
himself testified that if one had seen him, he had seen the Father.
Saying that Christ was in the “form” (outward appearance) of God is
simply stating that truth in another way. Unlike Adam, who grasped at
being like God (Gen. 3:5), Christ, the Last Adam, “emptied himself” of
all his reputation and the things due him as the true child of the
King. He lived in the same fashion as other men. He humbled himself to
the Word and will of God. He lived by “It is written” and the commands
of his Father. He did not “toot his own horn,” but instead called
himself “the son of man,” which, in the Aramaic language he spoke,
meant “a man.” He trusted God and became obedient, even to a horrible
and shameful death on a cross."
On this view, Jesus isn't just a man like any other man. He is the Son of God, the Messiah. So what does 'being made in human likeness' mean? My best guess on this view is that it means he carried himself as a typical man, the 'son of man' - a carpenter from a small-town.
So, from the OP:
"Since Jesus Christ was born as a human being like the rest of us, meaning He appeared as a man why was it necessary for Him to take the form of a bond-servant/man at Philippians 2:8 since He is a man already?"
He is born not just any man, but the Son of God. He has to empty himself of "all his reputation and the things due him" as the Christ, and follow God's plan.
Q: You say St. Paul's language isn't clear here re Jesus' divinity, but isn't he being clear at Titus 2:13?
A: Titus 2:13 is another contentious passage. See here for a Biblical Unitarian discussion of it.
Q: But how could he be born a man if he starts out a man?
A: This question seems to take a trinitarian lens to the passage. So he's in the form of God, then empties himself just before or during the incarnation, and so is born a man. This is not the unitarian view - this is not a temporal sequence referring to conception. St. Paul does not make the logical connections between the various elements clear here, but 'being born in the likeness of men' is probably a paraphrase or goes along with taking the form of a servant - i.e., “emptying himself” of all his reputation and the things due him as the Messiah and Son of God and living in the same fashion as other men. This is probably meant to refer to an on-going state of affairs (hence a 'mindset'), not an event that just happened once as in the trinitarian view.