From my reading of the article, it appears this vulnerability occurs at the a USB flash drive is enumerated, e.g., identified by the system. I do not think protecting against writes to USB flash drives would, in this case, have any effect, since the operation occurs when the drive is read from and not written to. What this attack actually reminds me of are similar exploits which were (or are) used against FireWire.
Your point about trusting external media is quite valid, and users with earlier versions of Microsoft Windows should verify AutoRun is turned off and fully patched. While that certainly won't stop all attacks, it will, at least, improve security.
I know the vulnerability does not care if the USB device is write protected or not. By write protection I meant it would stop the USB device from getting infected on the customers machine in the first place.. if that was possible.