It seemed to me like very hasty self defense, there's a lot of AI slop hate and Ars can't risk becoming known as slop when their readers are probably prone to be aware of the issue.
I don't think Ars thought they had a choice but to cut off the journalist who made the mistake, especially when it was regarding a very touchy subject. I don't think they had a choice, it's impossible for us readers to know if this was a single lapse of judgement or a bad habit. Regardless, the communication should have been better.
AnonC doesn't seem to be upset that the journalist was fired. The disappointment comes from Ars trying to brush this entire situation away by deleting articles, comments, and making no statement on their website.
All they had to do was write a clear and simple message saying that one of their staff was responsible, has been fired, and they'll take steps to avoid this in future.
Their actions so far just make me think they're panicking and found a scapegoat to blame it on, but they're not going to put any new checks in place so it'll just happen again.