Is it fair to say then that you believe some conference talks are incorrect or are incompatible in some sense with the totality of the views of God since they are are not all canonical?
If two conference talks contained conflicting messages (for the sake of argument we'll say they are from people of the same level, for example both seventies) how do you choose, or is it possible that you may disagree with both and have some third option?
I think where I'm trying to go is here: is it possible to be a) both a good Mormon and b) disagree with the church on this issue? Is there room for dissent without being evil or in sin?
And before I get blasted here by people who aren't colton (who I have a decent history with when it comes to discussing issues related to Mormonism, so I doubt he would take these questions from me the wrong way) I think it is extraordinarily difficult to cast me as an anti-Mormon. Please don't get defensive, I am truly asking in as respectful a manner as possible.
I absolutely believe that some conference talks in the past have been incorrect or incompatible with the views of God. I cited Elder Dunn's made up stories above as an example of that (although presumably the points of his stories still followed core LDS principles). As another example, the church "Gospel Principles" manual used to have a quote from conference by an apostle (if my memory holds; sorry that I forget the details) which said, "Fathers should prefer to have their daughters get murdered than let themselves be raped." That quote was found in the German version of that manual c. 1990, and presumably in some pre-1990 English version manuals as well. I recall distinctly because a fairly recent convert asked me then (I was a missionary) if that sentiment seemed right to me. Meanwhile, that quote has disappeared from the manual, presumably because current church leadership does not agree with it.
So, if a conference talk doesn't seem right to you, or if it conflicts with another talk, you choose by letting your own conscience (aka inspiration from the Holy Spirit) be your guide. As I said to the missionary in the story in my last post, when all is said and done you are responsible to God for the choices you make. So, do what you think is right and let the consequences follow.
(But, I would add, be very careful if your own inspiration takes you too far away from what church leaders are teaching. As I believe one of the speakers at conference said, there is such a thing as "inspiration" from the wrong source.)
Let me now address this specific question: "I think where I'm trying to go is here: is it possible to be a) both a good Mormon and b) disagree with the church on this issue? Is there room for dissent without being evil or in sin?"
As Trout said, sure you can be a "good Mormon" and disagree with church leaders. But I would say, only to a point. Taking Pres. Kimball as an example... when he said, "The Lord told me to remove the priesthood ban", to me that is clearly declaring the will of the Lord. "Good Mormons" sustain the president of the church as a prophet, and recognize him as the only person on the earth entitled to speak for the Lord. So if people disagreed with Pres. Kimball's change in policy back then, I would say that they had crossed a line and were no longer sustaining him as a prophet.
Would gay marriage be such a thing? Not necessarily, in my opinion. I could see a situation where a "good Mormon" might feel opposed to gay marriage on a personal level, but because of their overall world view of how the law should operate, might vote in favor of gay marriage. (Reference point: I recently had a Jewish research student who said that's the way he, and most of his congregation, view the gay marriage situation.) Actually, wasn't Steve Young's wife (I forget her name) in that exact situation? I don't think she was kicked out of the church, or anything like that, because she was actively against Prop 8.
(quick search) Yep, here it is:
https://www.sfgate.com/cgi-bin/blogs/nov05election/detail?entry_id=32216
https://www.ksl.com/?nid=148&sid=4686916