In the beginning was the Word, and the Word was with God, and the Word was God. He was in the beginning with God. John 1:1–2, ESV
I heard a sermon a long time ago in which the preacher defined a cult as any religious group that called itself Christian but denied the orthodox doctrine of our Triune God. That means that those who deny the Doctrine of the Trinity, according to that definition, are not Christians, but heretics.
The man-centered part of each of us, that is the flesh, rebels from such a strict “legalistic” view, but as our faith becomes more and more God Centered in all its aspects, that view becomes entirely justified in our hearts because as we come to know God as He reveals Himself to His children, we will not doubt His Word nor will we attempt to overlay His truth with “altered” truth nor will we add to it nor subtract from it nor take it out of context in order to make it more man centered.
If we compromised and did those things we would do so in order to become more acceptable to the majority and not be excluded and hated by the world and those who call themselves Christians, but who are really just part of the fallen world system.