With the exception of the Orthodox, who don’t accept the filioque (”who proceeds from the Father and the Son”) referring to the Holy Spirit, if you are not Nicean, you are not Christian. The Nicean creed is the fundamental statement of the Christian faith. It includes all of the basic beliefs of classic Christianity. If you don’t confess the creed, you are not a Christian. Flame away, if you like.
Nicea was a forced council called by an emporer who wanted peace among the Christian denominations. It was a political decision, not one based on irrefutable scripture or revelation. As such it may or may not reflect the truth. It does reflect accepted tradition but tradition is not given the same merit as scripture. And for every scripture quoted to support the concept of the trinity (which isn’t in the scriptures as such), there are others to support the idea that the Father and the Son are separate, though totally unified in purpose, beings. To decide that only those who accept Nicea can be called Christian seems to me arrogant and makes about as much sense as the Democrat(ic)s stating that because they won the last election, they are the only true leaders of the House and Senate and anyone who votes against their hegemony from this point on cannot be considered American.
In the Parable of the Good Samaritan, the Savior made the point that the true neighbor was one who acted like a neighbor. The true Christian is one who acts like a Christian in following the Savior’s example, in accepting Him as the only way to approach the Father, in believing that He died for the sins of mankind and redeemed us from death and Hell, in believing that He is the Only Begotten of the Father, and that He is our Lord, Redeemer, Savior, and God.
It is true that different denominations define the Savior in different ways. That is to be expected among so many sects and so many different interpretations of scripture, but I seldom hear of Mormons or Jehovah Witnesses or others condemned as non-Christian claim that they are the only real Christians and everyone else is a non-Christian.
I did not post this as a flame and I hope you don’t take it that way. I sincerely believe that Nicea and the other councils were part of tradition. Prostestants rejected the Catholic Church’s claim of the authority of its tradition and yet when a religion rejects tradition that Prostestants accept, they are pilloried and rejected as “non-Christian”. Again, the Trinity is one interpretation of scripture. The council, so far as I know, never claimed to received heavenly messengers declaring the Trinity, never claimed prophets affirmed their interpretation, never claimed anything except a majority vote at the stacked council. It is tradition and as such it is neither necessarily correct or sacrosanct as far as I am concerned.
I have no problem with people accepting a concept of the Trinity. I have a real problem with the Trinitarians claiming no one else can be a disciple of Christ except Trinitarians.