His comment didn't say they have Macs, he said they have Apple products. The dominance of the iPod makes it more probable that everyone he knows has at least one Apple product. Also, you assume that market share is evenly distributed in all demographics. I think the preceding discussion was about Apple's market share among tech enthusiasts, which I have never seen solid numbers on, but which seems, anecdotally, to be higher.
What does "own iPod" have to do with "is gamer"?
Loose correlation, (probably) not causation. It's obviously anecdotal, but thinking about the tech habits of people I know, it seems plausible to me.