Not at all, in fact it’s quite appropriate. The comment it was in response to an implication that all audio content was essentially equivalent, which it is not. Satellite radio has a number of technical advantages over terrestrial radio, as do cars over horses. They aren’t equal, thus only one satellite radio content provider is a monopoly.
Almost by definition you can’t have a monopoly on a non-essential good.
Love it as much as I do, satrad is a luxury good.
If it went away, I would just switch to listening my iPod full time.
How is an iPod not a competitor to, or a substitute for, satrad?
So what if the merger is blocked and, say, XM goes out of business. Now Sirius is the only provider of Sat Radio, and thus by your definition a monopoly. So should the government step in and dismantle them?