There is as I also believe, only one road to God, but consider just a couple of things on that. First is, how far down the right road a person has traveled [of course some may have been on the wrong road from the start.]? Some at a given moment after meeting the Master are babes in Christ and may know very little and some of what they know may be in error. Some others have served God for a long time and have matured. Not as much slack given to them by God I would hazard to say.
Second, would be what part of the Body of Christ a person is, or is to be? How skillful does a person's toes have to be in order to be a good walker? On the other hand, if a person is the hand, his fingers need a better dexterity than that of toes.
Can even a mature believer still have some errors in what he says or does or even believes? How many people, believers, have already moved from a blurred or dim or darkened vision to a "face to face" vision at any point in time? Does not God consider all of these factors more completely and with regard to any one of us than any man can do? Who but God has all the facts and is able to fairly evaluate them all about each and every one of us? Jesus, I believe, tells us about this here:
"But he that knew not, and did commit things worthy of stripes, shall be beaten with few stripes. For unto whomsoever much is given, of him shall be much required: and to whom men have committed much, of him they will ask the more." Luke 12:48
"Much is given, much is required"! Someone who is in error certainly in that respect has "less" then 100%. Assuming that the Trinity doctrine were completely in error, before rendering a final judgement against a person espousing it, would it not be necessary to know exactly what the man knew and believed in detail and why? This is why, I believe, Jesus also said this:
"Judge not, that ye be not judged.
For with what judgment ye judge, ye shall be judged: and with what measure ye mete, it shall be measured to you again.
And why beholdest thou the mote that is in thy brother's eye, but considerest not the beam that is in thine own eye?" Matt 7:1-3
We can and do have our own opinions and beliefs, but before we open our mouths in condemnation of another who differs, shouldn't we be absolutely that we have all of the facts about the other person and that our vision is not marred even slightly by a beam or even a mote of our own?
Then again...
"He that believeth on him is not condemned: but he that believeth not is condemned already, because he hath not believed in the name of the only begotten Son of God." John 3:18
Two things on that verse: One is who knows without a revelation from God that another person does not believe on him? Two is that the verse, to me anyway, clearly states that one who doesn't believe is already condemned. Why need we say anything at all, even if we believe the worst about the person? Is that not ultimately God's business?
What man has God appointed to condemn any other person openly to the world of men? Perhaps He has appointed some people to do that, but I have yet to meet one who satisfied me that he had been given that job by God. I could be wrong about that, but until I hear it from God, I will strive to stand back a bit... What you do, of course, is between you and God.