Personally, I use downvotes to say “I disagree with this and/or it is a stupid/bad/bigoted/etc take, but I do not wish to spend the time and effort to respond and get dragged into a text-based mudfight

So far, a great articulation of what (I guess) most downvoters are thinking.

with someone who is unlikely to speak to me politely, no matter how polite I try to be in my rebuttal.”

But I’m not sure you’re being honest with yourself here. Certainly not if you’re talking about my comments, which are always polite if sometimes a bit forthright because I’m a direct kind of person.

I like having a way to say “no, bad, stop that”

Nicely put, again. But then: why should your antagonist “stop that”? They should shut up just because you disagree with them?

We come back to the crucial element: civility. If one believes in free speech, and the right of others to have their own opinions and to have a voice, I still see absolutely justification for downvoting a thoughtfully expressed opinion.

I don’t agree with you here but I respect your right to have an opinion and I would never think of downvoting you for it. If that comes across as sanctimonious, so be it. I prefer to see it as just coherent with values. Which I’m sure you share, by the way.