I don't remember watching the Flash movie your brother made. But it takes (I think) 300 people's votes to get a submission blammed. So if your brother's movie got blammed, that means many people thought it wasn't good enough.
Why it got blammed, I don't know. There could be a number of reasons. Having absolutely no sound effects or music was a big mistake, though.
Did the movie have a preloader (that worked)? I've seen a lot of great Flash submissions under judgement, but they lacked a preloader (or sometimes even a simple "Play" button), so I had to vote lower than I normally would because of this. Without a preloader, the movie will appear blank, and so people will assume it's spam because there's nothing there.