I think we all wish that we could see the reasons people had for downvoting, but I've accepted that it's just like real life: people will disagree or dislike you and judge you, and you might end up none the wiser, and that's just how it goes.
I think this combination of phenomena, getting downvoted for going against groupthink as opposed to not contributing to the conversation, commenters trying to call out their downvoters, commenters accusing their downvoters of being sheep, is more illustrative of a different general issue: people have a tendency to perceive negative social signals as attacks. We all understand defensiveness as a phenomenon, but humans in general are also much better at spotting defensiveness in others than in themselves, so the calmness disappears when it's you being downvoted.
Downvoting as a mechanism seems to do an approximate job of social regulation at best, and I think that's specifically because the wisdom of the crowd is only good for some things and specifically not good for handling nuance or dissent.
My favorite are the people who demand sources for every assertion of yours, while making numerous factual assertions of their own without providing sources.
Bonus points for disregarding sources once provided, e.g."everyone knows Snopes and Politifact are fake and just anyone can write on Wikipedia".
* "The Pedantic Nitpicker". He will respond to your long, 50 sentence comment and say something like: "That one sentence said 'all' and should say 'some' because here is a counterexample. Therefore, YOUR ENTIRE POST IS WRONG."
* "The Sealioning Scientist". No matter what you say, she will ask for linked academic sources, and goad you into arguing, all while acting sincere and curious. If you fail to cite them, then obviously you are writing fiction, and she wins.
* "The Silent Downvoter". Skims through posts, looking for ones that violate some established groupthink or simply go against the current subreddit's zeitgeist, downvotes and sneaks off into the dark. Nobody knows their username because they never comment or explain their downvote.