This phrase is, or is close to, something that the character Gollum says, in the fantasy work by J. R. R. Tolkien, "The Lord of the Rings." A quotation--from the movie is--in part: "They're thieves! They're thieves! They're filthy little thieves! ... Sneaky little hobbitses. Wicked, tricksy, false!" (Gollum uses incorrect English). So it is by the author J. R. R. Tolkien. Of course I don't know who is the person who scrawled it in a public place.

(To someone who knows the book--or movie--the phrase reminds us of the personality and mannerisms of the character Gollum).