A member of the 4chan online community who insists on protesting against the Church of Scientology, usually while wearing a Guy Fawkes mask to protect his/her identity.
Protestfags are widely considered a large part of a phenomenon known as "The cancer killing /b/." This means that they are widely blamed for /b/'s decline in quality and popularity.
Newfag: DOWN WITH SCIENTOLOGY!!!
Oldfag: stfu protestfag.