Depends. If you use the Facebook App from the market then open the facebook-app and press the menu-button and then go to settings. Under the item contact-sync you can select which facebook-contacts are synced with your phone. There are 3 options (none, only contacts that are already on your phone, all contacts). Selecting none should solve your problem.
Another way to remove all facebook-data from your phone is:
Open the facebook app, press the menu-button on your phone and then press Logout.
Then a info box is shown which informs you that the logout will remove all Facebook-Data from your Phone.
If you use Moto's facebook integration then open contacts, select menu button, select accounts, select facebook, then remove account.
You will lose your facebook but then re-add the account but turn off the sync and don't sync with contacts. Hope this helps and is clear enough...alternatively, you can also change the display options to show only contacts with phone numbers also.