So the only thing holding you back from deleting a subreddit with tons of information, 25.000 subscribed users and what looks like a rather active and healthy discussion isn't that it would be a dick move to both golang in general and the community, but that you're not actually the owner.
Not attaching your brand to poor service is also part of managing a community.
If AWS started MITMing client HTTP connections and injecting code, would you be surprised people moved their official websites off the platform, even if a lot of people knew the old IP address?
That's not childish, that's not doing business with bad partners, and Im not convinced a space that started as official could ever truly be made "non-official".
What I mean is that the subreddit doesn't belong to bradfitz, or Google, or the golang creators.
It has never started as official because the creator was /u/uriel. The Google guys may have joined after, but the fact is that it is not their community. They're not even paying a single dime for it.
If AWS started MITMing my connections, absolutely, I would drop it. But the analogy doesn't hold because /r/golang isn't bradfitz's subreddit.
The proper and only response would be to drop moderatorship, leaving in a thread his reasons, and leaving /r/golang as it is. As it stands, the only thing stopping him from doing that is that the he's not the original owner.
And, you could also argue that when a community reaches a certain size, it doesn't belong to you anymore. It belongs to that community. To delete it is petty and childish.
Could you get any more childish?