This isn’t really a new phenomenon; it dates to the 1980s or even beyond. The canonical explanation is Eric S. Raymond’s How To Ask Questions The Smart Way.
It explains why more-experienced users of a channel may respond to some questions brusquely; and how to get past the problem.
You may have intended for this to be a “defense”, but it appears to be mostly a reinforcement of what many have already written in the critical pieces on SO. Your observations about what’s going on are quite accurate. Unfortunately, I believe the problem is that the behaviors you describe (and that others have also done) are indefensible.
Because a downvote, with nothing else, is lazy. It doesn’t help anyone, it gives them no way to improve the question. It’s a drive-by middle finger, it tells you that someone is unhappy with your question, but with no way to tell why. You’ve said “something is wrong”, but given no useful information to fix it. Honestly, it’s the SO version of “if you…