So instead of purchasing a game new for say $50 then the expansion for another $30 they waited till the set was $20 then purchased them all the while getting full use of a game that others paid full price for. That is stealing and is wrong in my book as they took something they liked then continued to play the game(although I know many people that did the same thing).
So what are you implying? That instead of giving any money at all to Blizard they should've just kept playing for free? If you read the guys post you'd have noticed he said that they didn't have the money to pay 50$ or more for the game because they had no jobs. Point is, they wanted to support the company that made the games, because they liked the game. Why did they like it? Because they got to try it and found out it was good. Why did they get to try it? Because of piracy.
Without piracy it's altogether likely (not certain, but likely) that these guys would not have bought the game at all. Moreover, your analogy of "stealing" is inherently flawed, because people wait for prices of products to drop all the time. I for example, would like to get a PS3 at some point, but I am not getting it before the price comes down a bit. If I end up buing it at a lower price in the future do you call that stealing?
My point is, since they guys had little or no money to spend on games they would've waited for the prices to drop anyways. Piracy "cost" Blizzard nothing - if anything it ensured that they bought the game.
Of course there are always going to be people who are just going to play for free and not buy anything, I'm not denying that. But those people are not the target audience of game manufacturers - you can't force people to buy stuff they have no interest in paying for. You can, however, create a product so good that a part of people who wouldn't have bought it otherwise will end up buing it*. Even if they buy it at a lower price that's still money made, not money lost.
*studies have shown that people who pirate music for example, spend, on average, more money on music than people who don't pirate. Source.