If splitting hairs, he originally framed the response as 'kill the messenger', implying there was no other reason for them be offended by it, misleading at least.

> Anyway I don’t know what’s going on here but “Sparkfun has ceased its business relationship with Adafruit because a guy called us jerks in a complaint about our CEO” would be hilarious

I agree, in isolation- it seems reasonable to end a business relationship with any rude or hostile partner regardless, but hiding such a decision behind a CoC rationale just for being called jerks would indeed border on 'hilarious'.

In this case, the claim is that the note was also sent to the ex-employee's partner's current employer, which enters less-hilarious territory towards borderline harassment, not a private HR complaint but public defamation.

Taken as one instance of a broader, ongoing pattern of targeted harassment of several individuals, the combined set of public complaints make the CoC reference not at all amusing.