> Would we still upvote those who deny climate change for discussion's sake, for example?

Why would you do that? There are plenty of opinions that are primarily "discussed" in bad faith, and that's one of the more significant ones.

Historically, if you look at past discussions, we've had great conversations by upvoting any comment that adds a new perspective to the mix.

If an ideal society wishes to eliminate climate change denial, for example, it won't be through silencing and stigmatizing their beliefs; it'll be through respectfully listening and debating.

As an example, I was rather unaware of the debate against climate change until reading a discussion on HN from people who were oft characterized as 'deniers.' One, for example, believed there were more immediate problems to be solved, and the other wasn't convinced by the science. It was a productive discussion, and I feel that everyone is better off having it, yet I fear that it wouldn't be condoned today without a mass of downvotes.

At this stage of the matter, it is quite possible that you fell for exactly the sort of bad-faith 'discussions' that pjc50 mentioned. Two forms of this are the repetition of thoroughly-debunked arguments and the injection of non-sequiturs (as I don't know what you are specifically referring to, I cannot say for certain, but most of what appears in this domain falls into at least one of these categories.)

I agree that there is no point in downvoting this sort of thing, but it is unfortunate if it gets upvoted by people who are not in a position to judge its validity. Scoring arguments on style is not the way to go (even if that is how the SAT essay is scored.)