Go to Prefs>Store, uncheck Show iTunes in the Cloud Purchases
If you still see them:
Go to your music, then View>Hide iTunes in the cloud.
Select each of your media types in kind (Movies, TV Shows, etc.) and go to View>Hide iTunes in the cloud
To further decouple your library from the Store/Cloud:
Go to Store>Turn Off iTunes Match and Turn Off Genius.
Go to Prefs>General, uncheck Genius
Go to Prefs>Store, uncheck Sync playback info, Automatically download album artwork, share info with Apple