This seems like a false dilemma. It assumes that because something is "doctrine," it is "negotiable" when it comes to our diverse opinions. (Actually, I think you are trying to refute that statement.)

Since "doctrine" simply means "teaching," I tend to think that every fact in the Bible is doctrine. It is all valuable for teaching. Some doctrines just happen to be more useful (or more important to a particular purpose) than others.

For instance, technically, some teach "false doctrine" when they suggest that Abimalech was a judge. Factually speaking, he was a usurper king, not a judge. This "truth," though, doesn't really draw us any closer to God or affect our salvation.

We all have a healthy aversion to divvying up the Bible into "essentials" and "non-essentials," and I want to stay as far away from doing that as possible. I think it is all essential, even Jesus' command (it's one of the clearest imperatives given) to wash one another's feet. The problem is that it is essential to the extent that our intellects understand it. It is not essential to the point of rejecting our brother who does or does not follow that command as we think he should.

In other words, one brother thinks he is following that command by whipping out a foot basin when he meets with his church family, and another thinks he is following it by serving his brethren in any situation he can. I believe the latter, but I don't think it's necessary to divide from a brother who believes the former.

Your dilemma is good to point out the fact that there is a difference between "moral doctrine" and other types of doctrine. I believe our morality comes from God, not the written words of the Bible. This may seem controversial until you think about it for a second...murder and adultery aren't wrong because they are written in the Decalogue. The Decalogue doesn't rule us today. Murder and adultery are wrong because they go against God's nature. Hatred is wrong for the same reason, not because Paul listed it as a vice in one of his letters.

God gave us all a conscience pre-formatted with a moral code, and Romans 1:18-32 tells us how God views those who reject the moral code that He made to be self-evident.

Where I'm going with this is that moral issues seem to be off the table as far as contradicting opinions go. Some legalistically argue from scripture that cocaine is OK because God gave us all the herbs of the field to use, but we know that doesn't make it OK. It should be self-evident from our God-endowed conscience that it is immoral to get stoned, drunk, or otherwise recreationally intoxicated.

When people reject the conscience that God gave them in pursuit of their own lusts, it's not a mere "difference of opinion." We do have an obligation to reject immoral brethren from our Christian associations, which would imply that we would not baptize someone who was continuing unrepentantly in immoral behavior.