Consistency is a big part of fairness, maybe the biggest part. Outsourcing "cancellation" decisions to the SPLC/ADL ensures that people are being consistently banned across all of the major social networks, after a full investigation by non-profits whose entire reason for existence is to do these kinds of investigations. They have, collectively, centuries of experience (and began long before the Internet existed).
Delegating also ensures that cancellations aren't done willy-nilly—the SPLC/ADL are not like a Twitter mob. They have (combined) over a billion in funds to investigate hate speech on the Internet, and to then advise the social networks that they are hosting hate speech—who then make the actual decisions to ban or not ban. Typically, they coordinate and all ban in unison, to avoid weird situations where someone is banned on one (or a few networks), but not all.
Obviously, none of this will feel "fair" to racist Whites, but there are places online (e.g. Gab, Bitchute, etc.) for them to speak freely to other racists where they won't be banned.
Delegating also ensures that cancellations aren't done willy-nilly—the SPLC/ADL are not like a Twitter mob. They have (combined) over a billion in funds to investigate hate speech on the Internet, and to then advise the social networks that they are hosting hate speech—who then make the actual decisions to ban or not ban. Typically, they coordinate and all ban in unison, to avoid weird situations where someone is banned on one (or a few networks), but not all.
Obviously, none of this will feel "fair" to racist Whites, but there are places online (e.g. Gab, Bitchute, etc.) for them to speak freely to other racists where they won't be banned.