You're ignoring (what was that about "intellectual dishonesty"?) the part where this is likely still archived by them, just not publicly accessible. You're also forgetting the countless screenshots and other documentation that exists of KF from prior controversial incidents.
Screenshots are not a trustworthy medium. Many of the articles published about Kiwi Farms contain significant factual errors and rarely cite sources for the claims they do make.
For example, the CBC recently published an article claiming that the Christchurch shooter "revealed his intentions (on Kiwi Farms) hours before carrying out the attack".
https://www.cbc.ca/radio/day6/kiwi-farms-online-forum-1.6565...
If you read articles from 2019 it was claimed that the gunman posted on 8chan shortly before the massacre. The claim that he posted on Kiwi Farms hours before is completely new and unsubstantiated.
Sure. That's why it's likely that - again, I don't know how this still bears repeating in this comment chain - IA still has the site archived, just not publicly accessible.
Because if it isn't publicly accessible it functionally doesn't exist, and what remains is a number of publications of questionable veracity.
Perhaps law enforcement will eventually be able to comb through the data, but there is no guarantee the general public ever will be able to.
It becomes a very questionable "trust us, they were bad" from sources that are demonstrably flawed.
(I am not saying they aren't bad, but from researching common claims like the owner is a pedophile and the Christchurch shooter posted on Kiwi Farms myself, it's clear that quite a few are exaggerated or not true.)