Network effect. If only few people leave, each of them has to face a penalty for leaving (in this case not being able to participate in one of Go's main discussion hubs). If the whole community decides to leave (or rather move), there is no such penalty.
This would be selfish, coercive and has 0 chance of working in the real world: I guarantee you there will be /r/golang2 or /r/gogophers within minutes of the the original subreddit being closed.
As mentioned by someone else in the thread: the subreddit was in existence before being taken over by the golang team, it was fine before them, it will be fine after them if they choose to leave.
Re:Deleting the golang subreddit
by toomuchtodo on Friday November 25, 2016 @11:20AM
(#13037737)
Because then people don't get to be righteous.
That's the best thing about righteous people. The ease with which they want to control and dictate the opinions and behaviours of other people.
How is this a big deal?
If you're not comfortable with a platform then by every means, don't use it.
...but why does what you think mean that everyone should be affected?