Perhaps gay is not a dirty word? (is included in your dirty words, but gay people should think otherwise.
A lot of people use the term "gay" in conversation as a synonym for "that sucks"; a friend of mine does it all the time. I don't think they mean anything by it.
To differentiate between "I am gay," and "Oh that's gay. I'm sorry that happened," you'd need a NLP with a politeness preference.
This is a very naive implementation to quickly get a handle of amount of porny documents. I intend to do some more work around clustering of porny words. I think understanding sentiment would be hard and involves a lot of labeled data, but that is a potentially very useful project.
Although I didn't realise this was meant to filter out a pornographic vocabulary; it makes more sense now.