I wouldn't really be taking a stand (changing his avatar to Mohammed)
The Raw Story article you cited wanted people to take a stand against what happened to South Park by drawing and posting pictures of Mohammed to a public website.
I said that I'd support it by posting a picture of Mohammed as my avatar at this website. I urged you to do the same thing.
Both Facebook and RKMB allow psuedonymous posting
So why is the former taking a stand and not the latter?