Two points:

• We don’t even know if that’s something the members of that instance agree on (say, a majority) as this seems to a decision taken by a single Admin. I would say that our little discussion here neatly shows that it can’t be claimed that all members of an instance agree with that instance’s Admin on everything (though if I didn’t agree with the general posture of your instance and hence of the Admin, I wouldn’t have moved there from lemmy.world)
• That subjectivity is one more reason to state it as the Op having been deemed toxic rather than is toxic. If you want examples that maybe most here are intimately familiar with at the moment, it’s the difference between saying that “an Hospital in Gaza was said by IDF to be a Hamas Base” or “Luigi Maggioni has been accused by the Federal Prosecutor of being a terrorist” versus “an Hospital in Gaza was a Hamas Base” or “Luigi Maggioni is a terrorist”.

One Admin making such a determination is hardly a strict process like a Judicial one (is supposed to be) with a beyond reasonable doubt determination.

That the Op was banned for what he or she wrote elsewhere than in forums of that instance also, at least for me, given extra weight to the idea that the decision to ban was an arbitrary by a single person who has a very specific power rather based on very concrete criteria and validated by other people.

Absolutely that Admin is Technically Entitled to do what they did (it’s their instance so they have that power), but that’s a whole different thing from the action having been Ethically or Morally Correct. Mind you, I’m not even saying it wasn’t, it might have been by chance, but the process that seems to have been followed - merely the opinion of a single human being who for technical reasons happens to have a certain power - is hardly something designed to maximize that chances of an Ethically and Morally correct result.

(Curiously, I would have found a vote by the members of the instance to be a perfectly acceptable and morally correct way of determining that they didn’t want that person’s presence in their instance, and in that case would have agreed with this last post of yours - though I still disagree that such process yield a beyond reasonable doubt assertion of the toxicity of the OP - but that doesn’t seem to have been what happened here)