If we are still talking about apostasy, it is not really a matter of what the apostate believes about God's definitions, it is a matter of what they believe about their fellows' definition.
If a person decides Christianity does not represent God's definitions of sin and judgment, but they once accepted it as that, even if only reluctantly, that makes that person an apostate. And I have found it is this matter of
sin and judgment and the character of God that causes people to become apostate and no longer 'believe', or not ever believe to begin with. It is the dividing line upon which people either believe or don't believe.
Consider - all denominations believe different things, therefore the definitions differ, you may claim to be right - so does everyone else. If you are over-confident, you risk driving apostates away from God. Is that a risk you are happy to take?
In essential matters of faith and salvation...
absolutely. If a person does not want to accept what the Bible says about sin, righteousness, and the judgment to come they should be clearly separated by those beliefs from those who do accept what the Bible says about that. I don't believe Jesus had any desire to dumb down the truths he taught in hopes of winning apostates back to a faith that even he did not endorse. Understand? IOW, to win an apostate back to the faith by changing it's fundamental beliefs about sin and the judgment of God to comfort and appease them is not winning them back to the faith. That would be replacing the true faith with a different one. Why would I want to do that?
Unbelievers are certainly not in a debate with God. They may well be in a debate with people who claim to know the mind of God but that claimed knowledge is arrogance in the extreme. Again, that presumed mind of God differs from denomination to denomination.
If there is one thing I know it's the fact that when unbelievers resist the Christian faith it comes down to their nonacceptance of what the Christian faith says is damnable sin, and God's authority and justice to pass judgment on it. And if you once accepted that definition but then later rejected it, that makes that person an apostate. This is the dividing line between the righteous and the unrighteous, the saved and the unsaved.
I have no problem with people believing that they know the truth - good luck to them. Where I have a problem is when their over-confident beliefs actually drive people away from God. I find that very sad. s a Christian, I always felt that it was my duty to draw people to God, not drive them away (See also my response to Davies about an 'evil heart').
From my point of view as a Christian who defends what the Bible says, what good is it for me to draw people to a lie?
You have to leave Christianity (become an apostate) to teach and defend other beliefs about sin and the judgment to come. And IMO it is very important that people do that and make it clear they no longer believe what the Bible says about sin and judgment and the God who's going to pass that judgment. That way the truth is preserved for those who do believe it and thus saved on the Day of Wrath.
But again, I say it is this matter of what constitutes damnable sin, and our responsibilities to the One who will judge that sin that causes people to be unbelievers and apostates. You can add as much window dressing to it as you want to make it look good and honorable and noble to reject Christianity or open it up to Biblically contrary beliefs but it always comes down to a person rejecting what the Christian faith says about sin and judgment and the one who will pass that judgment that determines if a person will believe and be saved, or not.
If people understood this when they have opportunity to witness they'd be able to cut right to the heart of the matter and not be distracted by peripheral matters of the faith that don't determine one's fate. Accepting what the Bible says about sin and judgment and the One who passes judgment is what determines a person's fate. Those who continue in the great debate about sin and judgment taught in the Bible will not,
and can not, be saved by the God of the Bible. Those who surrender completely to his judgments are the ones who are shown mercy and saved on the Day of Wrath. You can't resist God and expect to be saved by God. But so many people think they have some kind of chance on the Day of Wrath despite their objections to his justice. My wife thinks that. Do you?