Have you tried using command (apple key) & comma, (⌘-,) to get to LW's preferences?

http://www.gnutellaforums.com/160912-post3.html

Which version of LW are you using? Another way to stop seeing the shared LW tunes playlist is to open iTunes > Edit > Preferences > Sharing > untick 'look for shared libraries' > ok. This works for Windows so I guess it would work for Mac also