I understand that. If some one burns a flag with 49 stars is it against the law??? What about a "paper" flag? all of these issues are unresolved and would have to be resolved by the courts.
A ban would just make it harder to identify the jerks who think the US flag should be burned. Besides, they'd only start burning it symbolically. What if it's one white star on a blue background, and a couple of red/white stripes? A symbol of the symbol.
Prohibitions have been known to start fads that would never have cropped up if there hadn't been a ban.
Flag burning is political speech and nothing's more 1A-protected than political speech. We'd do more damage to 1A by a ban on flag burning, than the burners could ever do to Old Glory.
Maybe he's from one of those Islamic countries and doesn't know what an American flag is.