Part of "being nice" is accepting that people aren't perfect and just dealing with that, within limits of reason of course. "Assume good faith" and all of that. The phrasing of "cancer" wasn't brilliant, but also really not
that bad – certainly not bad enough to warrant removal from the Linux project. That's pretty draconian.
Code of Conduct is not about demanding absolute perfection and then selectively using it as a cudgel to beat people you disagree with. Doubly so since Hector's behaviour over the years has frequently been less than stellar, including in that very thread where he calls Hellwig's comments "distractions orchestrated by a subset of saboteur maintainers who are trying to demoralize you until you give up".[1] Yikes!
Using "cancer" to describe "it will spread everywhere and it will become unmaintainable" is not great, but at the core still a technical disagreement. Outright dismissing people's technical opinions and ascribing malicious motivations as part of a cabal is a mean-spirited and nasty personal attack, and essentially just an insult.
And it's really not "sabotage" to disagree or to be against something and being upfront about it. If that's "sabotage" then anyone saying "I don't think we should go ahead with this" is guilty of "sabotage".
[1]: https://lore.kernel.org/rust-for-linux/2b9b75d1-eb8e-494a-b0...