Are you really appealing to the authority of Scripture to deny the authority of Scripture?
I'm appealing to Scripture to contradict Luther's doctrine of "the Bible alone."
Luther's doctrine isn't in the Bible. That's a logical contradiction.
But disposing of Luther's false doctrine doesn't denigrate Scripture. In fact, it makes a reasoned argument for the inspiration of Scripture possible, since the Authority (Christ's Church) that wrote, preserved and canonized Scripture is infallible with regard to matters of faith and morals.
If we can trust Christ's Church, we can trust the Bible. If we can't trust Christ's Church, we can't trust the Bible.