And child porn is a great example -- and CSAM more generally. Today's fediverse would have less CSAM if the CSAM instances weren't on it. Why hasn't that happened? The reason that many instances give for not block the instances that are well-known sources of CSAM is that CSAM isn't the only thing on that instance. And it's true: these instances have lots of people talking about all kinds of things, and only a relatively-small number of people spreading CSAM. So not blocking them is completely in aligment with the Big Fedi views Evan articulates: everybody (even CSAM-spreaders) should have an account, and it's more important to have the good (non-CSAM) people on the fediverse than to keep the bad (CSAM-spreading) people off.

A different view is that whoa, even a relatively-small number of people spreading CSAM is way too many, and today's fediverse would be better if they weren't on it, and if the instances that allow CSAM are providing a haven for them then those instances shouldn't be on the fediverse. It seems to me that view would result in less CSAM on the fediverse, which I see as a good thing.