I won't pretend I'm great at sales, but this is directly contrary to the advice I get, which is you want to filter out people who are a sure "no" or not a match (eg, on budget) as fast as possible so you don't waste sales resources on them while minimizing the chance of leaving a bad impression from trying pressure tactics on someone who wont buy.
What am I missing? (I guess it could be intending to be unethical, but I prefer to assume I don't understand.)
This, so very much this. I love what Jeff Thull says about this... "always be leaving" (as opposed to "always be closing"). Make it clear to the prospect that you are not going to be the stereotypical sales-person who grabs onto them like a little pit-bull grabbing onto your leg, and who won't let go until they've been beaten over the head with a stick. Show them that you respect them, and leave as soon as it's clear that there isn't a good fit. Leave a good impression and later, when they do need your "thing" they're more likely to call you up (or take your call when you call again in a year).
If you leave a good impression, there's every chance they'll recommend you to someone who does need $thing, doing much of your selling for you -- you just have to leave them thinking "well, $thing wasn't right for me, but I'd do business with $person and $company".