Maybe he is off. Or maybe he did not approve of your reasoning.
At any case, if this forum is based on a justice system, then if one person changes their username then all should be allowed to. Unless the reasoning behind the action is so grand to actually change the law of become a permitted exeption.
I first told him that I would instead create a new account and asked for him to lock it as regular at day one (which he can do too) but he agreed to change my username instead (thankfully). I changed mine for privacy and security. I do not know about spodey's reasoning with him. But if he and I could under our particular reasonings, have our usernames changed, all who have the same reasons as us can or should be able to change it too.