Remove the ability for Non-Steam users to connect to you server.
That is what fysiks was trying to tell you. If you do that, then you can ban by SteamID and not have to worry about using this horrible method to ban someone
I do not browse the forums regularly anymore. If you need me for anything (asking questions or anything else), then PM me (be descriptive in your PM, message containing only a link to a thread will be ignored).