Regardless if it was a real admin or not, you should report who ever did that. Admins can't know everything that goes on, and they can't know everything another admin says.
Also keep in mind that even if every person who insults someone is immediately banned for ever, new people will come, and insults are very widespread on the internet.
But if the same person keeps doing the same violation and admins never even tell him to stop, that really becomes a problem.
