Getting Started:  
Log on to your Facebook Page, click the “Edit Page” button, and go to the “Manage Permissions” tab.
Option 1: 
Use the “Moderation Blocklist” option to list specific words you want blacklisted, like a competitor’s name or an unwanted discussion topic.
These comments will be displayed to Page administrators but not to the public, and will automatically be marked as spam.
Option 2:
The “Profanity Blocklist” option blacklists words that Facebook has identified as offensive to the whole community. You can choose the level of severity by choosing “medium” or “strong”.
You’re Done!
Click “Save Changes” and never worry about bothersome comments again.