I guess you think this is a witty thing to say.

we're already talking about a specific field.

No, I think you're trying to dismiss critics of Diamond without ever engaging with the actual criticism by blanket-accusing them of living in "an echo chamber" (and missing the irony of doing so on HN), without providing a shred of evidence.

It's a wonderful mental trick to convince yourself you're right without fact-checking yourself, not to mention dismiss any field of expertise that you disagree with, but it doesn't actually prove anything.

Well, I think you're trying to dismiss defenders of Diamond by saying "those people aren't published 'experts' in the field."

Which is, as you said, "a wonderful mental trick to convince yourself you're right without fact-checking yourself." They're not in our club, so they don't count.