As far as I am concerned, there are two differnces between using Felix and using Hussein.

1.  Motive - I think that felix was used as a goof with the sole pupose of pointing out his goofy middle name which more closely matched his goofy persona.  Hussein would be used with the purpose of making him sound like an Evil-doer, which is a worse motive.  

2.  Scope - I believe that the use of Felix was primarily in the left wing blogoshere and it did not show up in the Main Stream media.  If the use of Hussein was limited to the right wing blogosphere that would not bother me so much.  If it shows up in the main stream media (I already heard it on Hardball once) then that is a different story.