Why wouldn't Amir defend himself?
If someone was defaming you on another public forum, wouldn't you think it reasonable to defend yourself? It makes sense to defend yourself directly to the criticisms in said forum ...
The problem with ASR as of late is that such opportunity is not always given. A loud member, or a moderator, or a whole pack of them, publicly accuse an "inconvenient" member of disingenuity, of lack of knowledge, or of low intelligence, and then said member is immediately banned, with no way to defend himself there.
Do you expect to just be able to publicly criticize anyone you want, and with any level of misrepresentation, without any consequence or pushback?
As far as I can tell, this is absolutely the expectation of certain ASR moderators, and also of certain ASR members whose opinions are considered as the only valid ones by some moderators. That's the crux of the issue the OP raised.
As a medical analogy, this resembles an autoimmune disease. A healthy, balanced moderation serves a function similar to the one served by immune system. A hyperactive censorship, on the other hand, may be gradually killing ASR organism.