I forgive you because I know that you didn't understand this, but the man's name as far as you are concerned is Benedict. For you to refer to him by any other name isn't even an insult. It just looks like you don't know what you're talking about.
I realize that Wikipedia is not accepted as authoritative, in any official sense, however, I think its a safe bet that the article about Pope Benedict XVI/Joseph Ratzinger was written by the Vatican.
In that article—written by the Church—it states very clearly that the name Benedict XVI is actually a formal pontifical name—chosen, you are correct, as his first act as pope.
I’d be willing to bet you, that if Ratzinger has a driver’s license, or owns any real property back in Germany, the baptismal name “Ratzinger” is used—and has NOT been changed to “Pope Benedict XVI.” In the same way that Queen Elizabeth II was NOT named that before her coronation (rather her baptismal name was and still is: Elizabeth Alexandra Mary), and is still a Windsor, Pope Benedict XVI is still a Ratzinger, though his formal name—connected with is title as Pope, is Benedict XVI (not merely “Benedict.”)
It is no sign of disrespect to call a man by his family/baptismal/personal/legal name. Non-Roman Catholics are under no obligation to honor someone with a formal pontifical name—of an institution we do not recognize as actually catholic (universal)after all—especially in America, where our Constitution formally disavows titles (why we say Mr. President).
It may sound “stupid” to you, but non-Roman Catholics do routinely refer to Ratziner by his personal name—and that’s how the rules of English are established, by usage, not by a central hierarchical human authority—even that of popes.
So please do not presume to correct usage, or profess knowledge of things you really do not know.