If you are wondering whether or not your detective friend will confuse the derogatory form of dick with the slang term for detective, well, that depends on how much currency he holds in the parlance of English slang. As to dick being a pejorative for detective, that claim is dubious. Word Detective, citing the Random House Historical Dictionary of American Slang, has this to say about the word's origin (italics are mine):
The Random House Historical Dictionary of American Slang suggests an entirely different origin (different from the notion that "dick" is a shortened form of "detective) for "dick," one that I find very plausible. They trace the noun "dick" in the "detective" sense to the 19th century (around 1864) criminal underworld slang verb "to dick," meaning "to watch." This "dick" came in turn from the Romany (the language of the Gypsies) word "dik," meaning "to look, to see." This is significant because the Gypsies, originally from northern India, played a prominent role in the British underworld in the 18th and 19th centuries, and several Romany words (including "posh") percolated into general English usage during that period. One can easily imagine "dick" meaning "to watch" being transformed into a noun that means "one who watches, a police detective, etc." It is even possible that the popularity of Dick Donovan tales at the time contributed to the spread of the term "dick" among the law-abiding (and mystery-reading) public.
I would also add that, after reading a half dozen Raymond Chandler novels, I don't recall any implied meaning of "dick" that suggests its relationship to the derogatory usage we hear today. The most pejorative implied sense of the word I've taken away from detective fiction comes from the slighting way police officers use the term to refer to dime-a-dozen private eyes. In that way, the word "shamus" is also used equally pejoratively.