It's easy to help him leave facebook
Is he a windows user? (similar to below is possible elsewhere, but I don't have the know how).
open c:\windows\system32\drivers\etc\hosts. in notepad. add a line at the end that says
127.0.0.1 w
ww.faceb
ook.com
save the file. MAKE SURE that you choose "all files" as the file type so that the file is named hosts and not hosts.txt.
Every time he goes to facebook he'll just get "page cannot be displayed"