By the way, just for your information and not to challenge Trinitarian views, here is an interesting overview of why Unitarian Christians in the 19th century rejected the Trinity:
THE TRINITY.
§ 17. The doctrine of the Trinity, as stated in the creeds of all the so-called Orthodox churches, is this: that there are three persons in the Godhead,‹ the Father, the Son, and the Holy Ghost,‹and that these three are one God, the same in substance, equal in power and glory, but distinguished by personal properties. The Athanasian Creed is the most distinct formula of this doctrine. It says: "The Catholic faith is this, ‹that we worship one God in Trinity, and Trinity in Unity, neither confounding the persons nor dividing the substance. For there is one person of the Father, another of the Son, and another of the Holy Ghost. But the Godhead of the Father, of the Son, and of the Holy Ghost is all one; the glory equal, the majesty co-eternal." This doctrine teaches that the Father is God, the Son is God, and the Holy Ghost is God; and yet there are not three Gods, but one God. Each may be worshipped separately. Each has a separate work and office, which must not be confounded with that of the others; for that would be the heresy of Sabellius, who confounded the persons. But we must not say that they are three persons, like Peter, James, and John; for that would be dividing the substance, which is another fatal heresy.
See the "Westminster Assembly's Catechism," which is the creed of the whole Presbyterian church; the Athanasian Creed, still read or sung, by authority, four times a year in the Church of England; the Augsburg Confession; and the creeds of other Orthodox denominations. § 18. Unitarians reject the Church doctrine of the Trinity,‹
(a) Because it is unintelligible. Although many attempts have been made to explain it, none have proved satisfactory. It therefore remains, even by the admission of its advocates, a mystery; and a mystery is something unintelligible, and therefore cannot be an object of belief.
(b) Because the doctrine of the Trinity is nowhere plainly taught in the New Testament.
This is admitted by many candid Trinitarians. Thus, Neander, a Trinitarian, says of this doctrine: "It is expressly held forth in no one particular passage of the New Testament." (Church History, Torrey's translation, vol. i. p. 572.) Many such testimonies might be adduced. (c) Because the texts quoted in support of the Trinity are inadequate or irrelevant.
The famous text of the Three Witnesses has been shown so convincingly to be an interpolation, that it has been rejected by most Trinitarians and omitted in the Revised Version. The Baptismal Formula (Matt. xxviii. 19) and the Benediction (2 Cor. xiii. 14) are passages often brought forward as proofs of the Trinity. But in neither of them is it stated that the Son is God, or that the Holy Spirit is a person, or that these three are the one supreme God. That these passages should be constantly quoted as proofs of the doctrine of the Trinity shows that no real proof-texts of the doctrine can be found in the New Testament. They may seem to imply it to one who already believes that doctrine; but to those who do not already believe it they appear as a summary of the truth which proceeds from the Father, the only true God,‹through Jesus Christ, his holy child and the mediator of his love,‹and made part of the soul and life by the inward influence of the Divine Spirit. (d) Because there are many texts in the New Testament plainly opposed to the Church doctrine of the Trinity.
Such are the texts in which the Father is called the one or only God; which could not be said if the Son is also God, and the Holy Spirit God. 1 Cor. viii. 5, 6: "For though there be that are called gods, whether in heaven or in earth, (as there are gods many and lords many,) but to us there is one God, the Father:" Eph. iv. 6: "One God and Father of all, who is above all, and through all, and in you all." John xvii. 3: Jesus prays to the Father, saying, "Father! the hour is come!" and immediately adds, "This is life eternal, that they might know thee the only true God." Eph. v. 20. The Apostle directs the Ephesians to give "thanks always, for all things, in the name of our Lord Jesus Christ, to God, even the Father" (Revised Version.) If the Son were God, and the Holy Ghost God, it would be our duty to pray to them also. But all prayers are commanded to be addressed to the Father. See Matt. vi. 9; John iv. 23, xvi. 23.
(e) Because we know when and where the doctrine of the Trinity began, and how it gradually took form.
In the famous Proem to his Gospel John opposes the idea that the Logos, or Word, was anything different from God himself. The Word, he tells us, is God speaking, first, in creation,‹ "By him," God speaking, "were all things made." He refers here, no doubt, to the common phrases of the Old Testament,‹God said, "Let there be light;" "The Word of the Lord came to Isaiah;" etc. Secondly, the Word is God speaking in the soul,‹"That was the true light which lighteth every man that cometh into the world." Thirdly, the Word is God revealed in Jesus,‹"The Word was made flesh and dwelt among us." He thus teaches that as God speaks in creation and speaks in the human reason, he also speaks in Jesus more clearly and fully. But, as if to obviate the possibility of being under stood to say that Christ was God when he really says that God is in Christ, he adds, "No man hath SEEN God at any time."
This conception of Christ as a Logos, or Word of God, or a revelation of God, continued to be taught down to the time of the Synod of Nice (A.D. 325). The Apostles' Creed, which in its substance goes back to a very early Christian period, contains no trace of the doctrine of the Trinity. It calls God "the Father Almighty, Maker of heaven and earth." The Nicene Creed, in its original form, knows nothing of the Trinity. It calls Jesus "God," but speaks of him as God of God, meaning "God derived from God," and so makes his divinity derived and dependent. And it was not till the year 380, after much controversy and party strife, that the doctrine of the Trinity was established in the Church. In the year 383 Theodosius the Emperor threatened to punish all who did not accept this doctrine.
http://www.americanunitarian.org/manual.htm