So what is the problem here? Users expect Apple to support music that was purchased from other stores? Why would Apple do that? Do users expect Ford parts to work on a Chevy? A fake K-cup in a coffee maker? The wrong cartridge in a printer? Lots of companies insist on using their parts and consumers accept that as reasonable - why pick on Apple? Is it because they have the deepest pockets?
Wow. You took a bad car analogy and made it worse with other bad examples.
You might be thinking, why would this guy say my car analogy is bad?
Maybe because car parts, whether from Ford or any other manufacturer, actually do work on cars manufactured by other companies. Thousands of Ford and Chevy motors are running in Toyotas, Nissans, Dodges, etc. Not only motors but other parts as well. So there's that.
Keurig only recently DRM'd their latest coffee maker (like dumb asses since the DRM was defeated in short order). Before that, you could use any K-Cup type of coffee pod you wanted to use. Buy an older model and you still can. An incorrect printer cartridge won't fit in a printer simply because of the shape. An offbrand cartridge configured for said printer will fit, run, and not void the warranty since it's illegal for a printer manufacturer to even claim it will.
Lot's of companies want you to use their products, but they can't force you.
OT: Rogifan said it best. The security director should have never even opened his mouth. That's the lamest excuse I've ever heard. Whether Apple did it intentionally or not remains to be seen. I've no dog in that fight.
We didn't want to confuse you with too much information. Thanks Augustin.