Anyone can be called a Christian, even if they are not. This answer deals with whether one may deny the deity of Christ and be a Christian.
And he said unto them, Ye are from beneath; I am from above: ye are of this world; I am not of this world. I said therefore unto you, that ye shall die in your sins: for if ye believe not that I am he, ye shall die in your sins. - John 8:23-24
The limiter is given as whether a person believes that Jesus is (is he). The divide is over who men consider Jesus to be. Some say he is a prophet. Others say he is an anointed man or some kind of exalted one. Who is he? This is the question and salvation, that is to say "being a Christian", hinges upon it.
Jesus asked this very question of the disciples and Peter, speaking from inspiration of the Father and on behalf of the disciples, declares:
When Jesus came into the coasts of Caesarea Philippi, he asked his disciples, saying, Whom do men say that I the Son of man am? And they said, Some say that thou art John the Baptist: some, Elias; and others, Jeremias, or one of the prophets.He saith unto them, But whom say ye that I am? And Simon Peter answered and said, Thou art the Christ, the Son of the living God. - Matthew 16:13-16
So we know (from God, through Peter) that Jesus is Christ and that Christ is Son of Living God. Peter also writes that it is the Spirit of Christ which was in the prophets testifying of the grace and salvation which was to come.
Of which salvation the prophets have enquired and searched diligently, who prophesied of the grace that should come unto you: Searching what, or what manner of time the Spirit of Christ which was in them did signify, when it testified beforehand the sufferings of Christ, and the glory that should follow. - 1 Peter 1:10-11
The same Peter also wrote that it was the Holy Spirit (of God) by which those prophets spoke:
Knowing this first, that no prophecy of the scripture is of any private interpretation. For the prophecy came not in old time by the will of man: but holy men of God spake as they were moved by the Holy Ghost. - 2 Peter 1:20-21
Thus, in Peter's mind, the Holy Spirit of God and the Spirit of Christ are the same. Holy men of old spoke by the Spirit of God ... by the Spirit of Christ ... by the Spirit of the Son of the Living God.
This is not the only time in Scripture where the Spirit of God and the Spirit of Christ are conflated. It is, however, striking that the same one who received and declared the revelation (from the Father) that Jesus is the Christ, the Son of the Living God is the one who later had no qualms about conflating the Spirit of Christ and the Spirit of God.
It is not primarily an intellectual exercise to receive and declare as Peter has done: The Father in Heaven of the Son on earth by the Spirit of God/Christ.