If you or I were going to write the story of the redemption of all mankind, how would it read? Who would have a part in it?
Of course, only the most morally upright and courageous people would be the heroes. The weak and double-minded would be the "goons," who would waver between good and evil, but ultimately be fruitless in their efforts. Surely the most evil people be the enemies who are thwarted in the end. Similarly, when we read the Bible, we also have the courageous heroes, the weak minded "goons," and the evil villains.
Most of the time, we can sort out who is what; our heroes behave like heroes, and the villains like villains. But here's one place where your version of the story might differ from God's actual plan: In reality, sometimes our heroes don't behave like heroes, and may even do things that seem villainous.
It's a difficult issue that has disturbed many the Bible student. Is God "okay" with having those kinds of people carry out His scheme for redemption?