I’m of the opinion that if a rename is required, user input should be prioritized. Renaming an account immediately, with a mail to the player explaining the issue with his previous name is not the best way to deal with this situation, but it could be worse. However, not allowing that same player to request a name change to something they can identify with immediately following the corrective action is wrong, in my opinion.
I understand his new name is an anagram of his original. This is not enough. You cannot call this ‘punishment’ for having an offensive name. Offensive names are trivial, as pretty much anyone can find offense with anything. The issue IMO is just the plain fact that you changed this account name without his prior knowledge (as far as I’m aware) and did not give him the chance to provide input as to what he would like to change his name to. Even now, when he does ask to have his name changed, it seems to be shrugged off with a dismissive gesture. This isn’t right.