Super Nothing
Member
If the minion you used shadow madness on has life remaining or you can't kill it, then you've effectively used the brewmaster to both remove your opponent's minion from the board AND draw yourself a card. So let's say your opponent has a 3/3 and a Tazdingo. If you Shadow Madness the Tazdingo, kill the 3/3, and then return the Tazdingo to your hand, then you've effectively spent 6 mana and 2 cards to remove 2 of your opponent's minions, put down a 3/2 of your own, AND you've drawn yourself a card.
That's the absolute best cast scenario. More often than not, you're just going to steal a minion and use it to trade with another minion. Putting it back in your hand isn't really adding benefit most of the time. Sludge Belcher and Shieldmasta are the only cards worth putting back in your hand, and I don't think that justifies including Brewmasters in your deck. Is he doing anything else with Brewmasters? Because it seems like those are mostly dead cards if you don't have a viable target to steal or don't draw it when you need it for the combo.