I certainly agree that if you are unable to distinguish a fake from the real thing, you probably shouldn't buy 2nd hand. If you have no knowledge of something, be it a watch, a warhol painting, or a hot security - it would be advisable to consult someone who does know first.
On the other hand, if you are like most watch aficionados (who bother to self-educate) and can spot a fake a mile away, it would be silly to ignore what is probably the largest 2nd hand luxury watch marketplace in the world.
Further, there are at least 10 major second hand dealers in HK who are long-established businesses and are intelligent enough to not commit commercial suicide by selling fakes. HK is a popular shopping destination for aficionados on the big fan sites like the rolexforum.
As to the advice to buy a fake - I guess it depends on who you are trying to impress. It might impress the shopgirls, but as a boss, I'd much rather hire someone sporting a Casio, then someone flashing a Folex.