Wow. That's surprising. I thought he was a reasonable guy. The people who claim that every pirated title wouldn't have been bought haven't thought about it much, are wrong, and shouldn't be adressed with anything but an explanation -- certainly not an insult.
Most pirated copies of a game are indeed most likely downloaded by people who wouldn't have bought it. 10-20% might be people who would have bought it.
A lot of people download every single game, movie, etc they can find, only to store it on a harddisc.
Say you're a pirate -- you've downloaded 1000 games or more; in most cases, you wouldn't have bought much more than 10-20 of those. Most pirate circles are made up of collectors; people who download stuff simply for the sake of collecting.
A certain site does mainstream pirating a bit, but you also have to consider the significant amount of games with malfunctioning cracks, no cracks, games with complicated installation instructions, so it's not like even the number of downloads from that site equals a 1:1 play ratio for the people who do want to play, in addition to the collectors, the testers that make up the overall numbers.
Yeah, it's the act of downloading a full game itself that might prevent a sale, so a malfunctioning downloaded title isn't necessarily a valuable argument in this, but my point is that it's a number of people who download it, can't get to play it -- so the overall "downloads" might actually be some of the "legal" buyers, in addition to the testers, the word of mouth pirated titles will spread, the genres/developers/series people might be introduced to, etc.
There are lots of ramifications to this. Based on how well the industry is doing, I don't think it's a good idea to tamper with its ecosystems.
In regards to the Xbox One, I think it's a big mistake to try and eliminate used games, or the way used games work now -- it will prevent collecting games, and contribute to even stricter rules. I think the overall money poured into the gaming ecosystem by collectors alone is significant.