Let me speak slowly. If you've got 8 rotten apples and 16 good apples, then the probability of getting a rotten apple randomly is 8/24 (33%).
Probability (X or Y) = P(X) + P(Y) - P (X and Y - case where both are scum)
8/24 + 8/24 - 1/24 = 15/24 = circa 63%
So, with two players you get almost double the probability that one is scum.