"Filthy fucking casual n00b fag" originated from Collegehumor's "The Adventures of Butthurt Anime Fan".
DJ S3RL created a song using video and voice clips from the video called "Casual N00b"
It seems to be used in a sentence as an insult against people that think anime or a certain show is perverted.

S3RL - Casual N00b --- watch?v=Kzv0FVKcZ8A
The Adventures of Butthurt Anime Fan --- watch?v=8mQScjlXbBE

A cultural and aesthetic mind-state that prioritizes making money, even as an “underground” or “radical” creator. The work isn’t made for money, but it’s the money that matters the most.