It hurts all miners indirectly, including the one doing the sabotage. Imagine you are doing this and manage to bankrupt a pool because its fees don't cover its expenses. Imagine it's a big pool like slush - confidence in bitcoin will drop and make even make other pools decide to quit the business. Price of bitcoin goes down... saboteur loses too.
But saboteur earns more than he loses. This is often the case with sabotage. Think of an exaggerated scenario, where the saboteur simply takes 50% of the pool's revenue for herself. Although she loses a bit of her own revenue, she gains enough to make up for it.
