I don't really mind the 'police' on CL, some of them are pretty amusing. If they're right it may save a sucker some money, if they're wrong the only people who would be influenced are those who wouldn't know enough to appreciate the item anyway.
What does get me with some people on CL, is they'll post something and when you respond, they'll send you a link to an Ebay auction, or some commercial resale shop a couple hundred miles away. Happened several times to me. I normally flag them as prohibited, and hope everyone else it happens to does the same.
Some people are just impatient I think, A while ago I was looking for another sailboat, and found one on CL emailed about it. The next day I checked email, and had two responses from the guy, dated a half hour apart, sent an hour before I checked, first one had minimal information, no address or phone number, just "three blocks north of the light in *town name*, turn left go straight till you'll see the boat in the yard" second one (only a half hour later!) said "If you're not interested why in the F waste my time" That boat was relisted twice, and still sits at his house, so I assume it was business as usual with him.
Ken.