If it IS optional, then there should be a clear way to REMOVE it, and while I have not looked at the situation long enough to find out how to remove it, I did not see something as obvious as an 'uninstall-mono' script.
If you run "wine uninstaller" and you have it installed (which you probably don't), it will show up in the list as something you can remove.
http://wiki.winehq.org/Mono also has a command line to remove it that will work for the foreseeable future.