Earlier quoted context omitted.
Most mods (who oversee the generation of new content) use the API because third-party apps offer superior mod tools. Instead of thinking about "shutting down third party apps" think about it as "asking your volunteer labor to do the job on hard mode". You can see why those people might get pissed off.
Do you have a citation for the claim that most mods use third party apps?
And I should have added some cutoff there. It's mods of large enough subreddits.
But why else would the mods be so up in arms?