I feel like this is not the whole story.
I don't consider this Amazon acting against unions, when it's more likely typical subreddit curation. There are other Amazon subreddits.
See, for example, r/starbucks and r/chipotle — many discussions here are employees talking about their work experience with customers occasionally poking in and chatting, there isn't a mob of people living and breathing Starbucks and Chipotle. In contrast, r/AmazonFC makes it even more topical and therefore more likely to attract an employee heavy userbase more than the average sub.
Different subreddits have different standards. Reddit has many subreddits that are very similar and have wildly different rulesets and prohibitions. Reddit isn't some greater commons of expression. This is the source of much of the drama and why subreddits often fragment into slightly more niche shards, all the time. It's just the way reddit has been for as long as I've known about it. The idea that Amazon has some overriding control of that particular subreddit seems unlikely with the kinds of whistleblowing that goes on frequently there. shrug
Could you elaborate on the "laugh" here?