Well the problem is, he's already driven up to price of the coins a little bit, by his buying activity before he even announces the coin.  So he is always guaranteed to win as long as he sells early and people continue to listen to him. 

So in theory, yes you could profit a little bit, by doing the opposite of what he says, but at some point even you would lose that, because he's starting to even lose respect among the hurr durrs.