In the betrayal at house on the hill rule book it says the traitor gets an extra turn on the monsters turn but what if there are no monsters in that haunt does the traitor still get the extra turn? Also is there a post somewhere that could help balance some of the haunts?
The traitor does not get an "extra" turn. Rather, he gets a turn to control his own character, and then the monsters get a turn, in which the traitor controls what they do. So if there are no monsters in a given scenario, then the traitor just takes his normal turn, once, and nothing happens on the "monster turn".
After the traitor’s turn, any monsters controlled by the traitor get a monster turn. (This means that the traitor gets two turns: one for his or her actions and one for the monsters.) Then the first hero to the left of the traitor takes a turn, and so on.
So while it does describe the traitor as getting "two turns", it is also clear that the "second turn" is the monsters' turn, not actually the traitor's turn.