My stance is: "Cancle culture" does not exist. The behaviour you describe existed before and there is no new development, that indicates the need of a new word. Death threats are not okay and that's totally independent of them being within or outside of something you call "cancel culture". And criticism doesn't get more or less reasonable if it is framed with "cancel culture".
I'm from germany. Here the phrase had a short burst of infamy as a comedian ("Dieter Nuhr") claimed people want to "cancel" him. By now the word is rarely used. And the discussion is better for it.
The only successful "cancelling" I witnessed was a left leaning twitter account, that was about fascism in austria. The woman behind it got death threats against her children and deleted the account. I think the use of the phrase "cancel culture" in this case is playing down the problem.
And if public figures try to silence criticism by the use of the phrase, than it's playing up the problem.
When and where - if ever - "cancel culture" is a useful term I don't know.
It is interesting you call it the "master vs main" debate. The problem is the combination of the words master and slave. You - maybe unconsciously - left the word slave out.
And there is not really a debate. I do not believe anybody was bullied to change that. It was a decision that was made independently. And now in the aftermath people shout about it as if it is utterly impossible that this could have happened without some mobbing or a big "culture" that made this a unjust decision. Because: "I know not a single adult that like that change." Well, maybe the majority likes it. The majority just does not participate in online discussions, so it's invisible. Hard to tell.