This is in response to your added question about the value of a Stack with repeated answers, and your concern about us or yourself just getting answers to everything of “don't do that”.
We don't actually want answers that just say “don't do that”. They're low quality. You'll be right to call those out if we get them. They don't provide actionable solutions to real problems. They're along the lines of saying “the GM should figure it out” or “it's an imagination game, just make something up.” Such answers should be downvoted, helped to improve, and/or flagged for moderator inspection and probable removal.
And of course, any answer which belittles the querent or otherwise violates our Be Nice guidelines is inappropriate, regardless of its answer-ish-ness. We're also not interested in “you're playing the game wrong”-type answers since we embrace a plurality of playstyles, and sometimes an answer that only says “don't do that thing” is falling into this unwelcome area.
The frame challenge guidelines don't make any of that go away. They're an extrapolation from the general advice in our help pages that say:
What, specifically, is the question asking for? Make sure your answer provides that – or a viable alternative. The answer can be “don’t do that”, but it should also include “try this instead”. [...] Brevity is acceptable, but fuller explanations are better.
These guidelines specifically demand that every "Don't do that" needs an accompanying "do this instead," preferably with an explanation of why the frame challenge is necessary. It's the "do this instead" that adds new, useful content to the Stack and makes a frame challenge a Stack-compatible answer like any other. Kviiri mentioned the XY problem in their answer: if we determine someone has a deeper problem, and we want to refuse the question they asked in an attempt to solve that deeper problem, we actually have to provide a solution to the situation.
To the original question you brought up:
This question, for example, has people immediately saying "don't" instead of just answering the question. Why? Why do people try to say "don't" or similar things instead of simply providing an answer to the question that was asked? Why does there need to be discouragement for certain courses of action just because it might not be a course of action other individuals might agree with?
Kviiri's also pointed out accurately in comments that the querent was looking for general guidance in how to handle this situation. Here's what they asked us:
My question is, as a new and hopefully long-lasting DM, how do I kill off a character? Do I make it fair? Is it better to instill the idea of hopelessness? Or am I overreacting and should let him play?
The whole “let them just have their character, and adjust the plot to fit them into it” is pretty reasonable along the lines of “you're overreacting, let him play”. The answers are also telling the DM not to kill the character off, but they're not just stopping at “don't do that” — they're going into depth on explaining how to resolve the problem sitting at the heart of that question: “there is a character who doesn't fit my plot, and I don't know what to do about it.”
So: we're not going to wind up as a database of answers that just say “don't do that thing” without providing actionable solutions. If we are getting those answers, please raise those to our attention. If you are encountering people largely trying to tell people their playstyle choices are wrong, please bring it to our attention (and bear in mind there's a difference between “that playstyle is wrong because I disagree” and “don't do that because it will get people genuinely hurt, and you appear to not be aware of this”).
You mentioned in comments you had a campaign with lots of player vs player activity. If you happen to be in that situation again, and want assistance handling something in that situation, we're not going to give you answers of “stop doing that” which decline to further attempt to solve the problems you're experiencing, and if you do get those, I'll hope for people to be raising it to our attention.
That said: if you want to attempt to change our meta policies around frame challenges, the correct approach is to visit our meta post for that policy — How do we handle a desire to challenge the frame of a question? — and write your own answer to that question so we can see and understand your proposal for policy on this issue. We can make only loose inferences about your own perspective through the questions you're asking and the issues you've raised in comments, but can't understand your full stance from them. We get you strongly disagree with something in how we're handling things, but responding in comments about how you disagree isn't going to create policy change on its own.
I can't promise your proposal will be received well, and I'm concerned there's something you're missing in our quality requirements around these answers. I'm also concerned about the broad generalisations you've made, which aren't backed up by evidence or may even be contrary to evidence (our body of player-vs-player conflict questions is not full of “don't do that” answers). We deal best in resolving real problems that demonstrably exist, which means generalisations should also correlate with substantial evidence. For an example of a question that successfully demonstrated a generalised problem and resulted in concrete change to our practices, see: The gremlin in our answers: "Fate is narrative" answers to mechanical Fate questions, which brought up a problematic answering pattern in our Fate questions which was corroborated by substantial evidence to show us (a) that the problem was real, and (b) what the problem was like in practice.