"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
Dude, this dude doesn't understand the whole casual fucking thing. "Think of me like a coupon book where you get one a month. You've already used this month's, holla back in July!" That how Dave rolls.