Neutral 3rd party observer here.
Firstly, I agree the question should be closed. I'm not entirely sure that as a Duplicate was strictly the right reason, but I see why it was chosen.
The question stems from the same incident - the meta-answer (heh pun intended) to both questions could be considered so similar as to make the questions essentially duplicate.
What I mean is - if you ask 'what is 2x2' and 'what is 6-2' - They are both different questions - but since the answer is 4, they are functionally the same.
People advising how to be more assertive or disagreeable or how to professionally set clear boundaries is the answer to both questions.
So even though the questions are different, the functional answers are the same.
Now, if I were to distinguish the latest question from your original, there is a unique question that I think you've asked...
But as pointed out in the comments, the Interpersonal SE is the right location for that question, not WP SE.
That's my take on it: I see the reason why it was closed, agree it should be closed, have a minor quibble on the reasoning - but think it was valid.