That protester MM is from "Anon" which is basically a unofficial section of 4chan.org (which is the worse place on the internet). They have adapted the Guy Faux mask as their official symbol and use it for protesting purposes. They hate Scientology and were the ones to take down their official website a few times. They got the use of the mask from "V for Vendetta" (The first picture of it from Jetee's first post is from the movie).
Here for more information (NSFW).
(I'll edit and post a pic later)