Christians are not required to accept the Deity of Christ or the trinity the moment that they become one, but in time their growth as a Christian reaches a point where the knowledge of it is put in front of them and that can be the crossroads where they and God can part as when they openly reject such things they then are straying farther away from who God is and end up having to sooner or later replace God with a facsimile of him to suit their error ridden theology. It is one thing to be a lay person and personally disagree with the trinity and keep it to yourself yet for the most part adhering to the other core tenants of Christianity but another thing to be a teacher or leader or evangelist and pass on your error to them. Some people I think can be Christians with error ridden understanding of Christianity while others this understanding when false becomes a stumbling block to their walk with God. If we look at the 12 apostles when Jesus himself asked the 12 "who do you think I am" did all 12 blurt out the doctrine of the deity of Christ? No., only one did and Jesus instead of scolding the other 11 who didn't immediately jump in he congratulated the one who did.
The Gospel doesn't mention the deity of Christ directly, but as one studies the trinity one can see it indirectly in even the gospel. For God so loved the world "HE" gave his only begotten son for who soever believes in "HIM"........ which "HIM" is being talked about here? Is it only Jesus, or God.... I contend believing is in the trinity because without it you are either believing in God OR Jesus...... NOT necessarily BOTH. If you continue in this verse you will see eternal life is mentioned and thinking through it you still have "He" and "HIM" as the giver of it... which one gives eternal life? It has to be both otherwise you are believing in one for belief and perhaps the other to give you eternal life which makes for interesting problems.