I don’t disagree with you, but if we’re talking about the wisest course of action here—assuming what you’re saying is true—it would be to resolve the matter privately and abstain from publishing this blog post in the first place. Perhaps publishing the letter is an escalation, but so is this. It’s just passive aggressive.
While I haven't followed this situation, I assumed based on this...
> we have temporarily stopped publishing on the Adafruit blog
That they needed to explain to their audience why they stopped publishing on their blog, and I inferred they might have previously mentioned on social media that an article was in the works, as many blogs do (which might also explain the demand letter). But I don't know for sure, and apparently neither do you.
The only difference is I didn't demand any documents, post uninformed speculation or "reasonably assume" lack of compliance with my demands would be "unclean hands" and "passive aggressive" behavior. I clearly need to work harder at being a more engaged uninformed bystander. I haven't even slung any accusations or roused any rabble yet.