I hate how people make this into a black/white issue. Its not.
Used sales may not be piracy, but they are much more likely to be a lost sale. I know there have been many times I went to a store with the intent to buy a specific game. If they had it used, I got it used, otherwise I bought it new. That was clearly a lost sale because of the existence of the used game, and hence they are receiving less income for their work. Every use game sale is not a lost sale, but a significant percentage of them are. The idea that the companies want to minimize lost sales should not be taken as a sign that they are evil. Theoretically, if they can make more money, they can spend it on making more/better games, which would benefit us as gamers.
One big difference between a video game and many products is the lifespan of use. A video game is something that you play through, complete, and you are done. Its remaining value to you is low- non-existant if you never pick it up to replay it. With a car, its value to you is continual. You will use a car pretty much everyday, and if you sell it, you are losing that value. If you have a shirt, you will wear it on a regular basis, and get continued value from it.
However, on the flip side, if you sell a used game, you are probably going to turn around and buy a new game with that money. A person selling a used game is probably a gamer, they are in a game store at the time, and they now have more money. The producer has gotten their cut of you buying that game, and now you are using part of the cost to buy a fresh game. Hence, the presence of the used game market also increases sales, so its net effect is much smaller than you may initially think.
However, regardless of the impact of the used game market on their bottom line, the fact remains that the publishers are damaging the value of the games in an effort to combat used games and piracy, and as their customers we are perfectly valid to be upset about it. If our ire cuts into their profits more than used games were, then they will stop. Unfortunately, they are most likely to pull these stunts on the AAA titles we have been waiting months/years for, and are loath to actually pass on playing the game because of it. Our desire to play these games means we will actually put up with a lot of BS, even though we may loudly complain about it.