It's because of a 'hide the taste' vs 'taste the taste' distinction. We taste things less well when they're cold. Try ice cream when it's warm, for instance, and you'll probably be nearly disgusted by how much sugar is in it. You can do similar things with acids, which is one reason (not the only) that you'll see sweet foods have a lot of acidic ingredients added. Your brain gets the same amount of 'sugar signals' while you don't notice the cloying sweetness. Guarantees satisfaction and a mild addiction. Really mild, but still. Anyway, back to the point. American beers, which have somehow dominated the cultural awareness of beers, are shit, taste like shit, and are thus marketed as 'refreshing' by brilliant marketers who have convinced people they need to be served below freezing. See the coors light blue mountain gimmick for 'when the bottle is at 29 degrees!' A good beer, that actually has had time and effort put into its composition, should, at best, be consumed just below room temperature. Warming it up lets you actually taste the effort that the brewer/vintner/distiller put into it.

Ok yeah, warm... That person said "hot beer," which is different than warm beer. Important distinction if you ask me.