Interesting and important question. I don't want to add specifically to what I and more crucially many others have said on voting here. There are many such threads. We're not long out of Ganging up with downvotes. How can we discourage mob behaviour? I hope it is fair to say that almost none of the participants in that thread are likely to feel that it went well or pushed anything forward. A minority of those posting feel very unhappy at some aspects of voting on CV. Even the rest should not be happy that those members are unhappy, regardless of not sharing in the gloom. But: to restate what is not a personal opinion, but a fact of SE: there are grounds for downvoting and anyone with enough reputation is at liberty to exercise downvotes. That's not to say that all downvotes are appropriate, but who decides and how do they know? Political allusions are tempting here, but anyone reading this will be smart and well-informed enough to think of their own.
Your general case doesn't stand or fall on your examples, but that's your specific evidence, so I will add some comments.
At the time of viewing each question I see this. Clearly each thread may change, not least because of the Meta effect of being mentioned here.
PCA 1 vote up, 1 vote down. 2 answers, reasoned comments. What's to remark on?
Regression for trend 1 vote up, 1 vote down. Reasoned comments in response; the OP has yet to improve their question. The question is not obviously doomed, but could go either way.
Uber question 1 vote up, 1 vote down. Put on hold. @DJohnson was among those voting to put on hold. I didn't participate, but I have to agree with the decision, although I am puzzled by the stated grounds. The question is in my view off-topic and/or too broad. But it is often true that a question that won't work well here gets close votes on several different grounds. The OP did receive some reasoned comments.
Harsh, like rude or sarcastic, is what the other guy is said to be, and virtually always unnecessarily so. Everyone knows irregular verbs of the form: I make fair comments; you are sometimes contentious; he and she are often downright obnoxious. But I have no axe to grind as defending any votes, comments or answers on the stated threads. I can't see anything here there that is harsh, or uncivil, or inappropriate.
The downside of CV is the downside of any technical forum I know, a long tail of questions that don't seem especially clear or interesting or answerable to many of those active in answering questions. Old story this, but no one is paying us to do this or obliging us to give our time this way, or to answer what we don't want to. Moreover, there is not much value for the forum in a large fraction of threads that do not or will not get anywhere far for the benefit of others. I don't disparage sympathy for those who might be discouraged by zero or negative responses, but a forum like this is not a help line. No one is entitled to an answer.
Socratic dialogue worked really well in the Socratic dialogues. It doesn't usually work well here. CV is in a mature phase where it's actually quite hard to ask a good new and specific question. It's also vulnerable to the postings of those who will not read or do not understand the generic advice displayed (e.g. on software-specific questions). I wish it weren't so.