Who said, "English is a language that lurks in dark alleys, beats up other languages and rifles through their pockets for spare vocabulary"?

The correct, complete quote appears to be:

"The problem with defending the purity of the English language is that English is about as pure as a cribhouse whore. We don’t just borrow words; on occasion, English has pursued other languages down alleyways to beat them unconscious and rifle their pockets for new vocabulary."
--James D. Nicoll

See, for example,
http://en.wikiquote.org/wiki/James_Nicoll