Life isn't always as simple or cut-and-dried as we'd like it to be. In everyday life, normal people have to make decisions based on their own judgments and values. This requires thought, the ability to act on your decision, and to live with the consequences.
Cults often devise ways to "relieve" members of the need to make such tough decisions as whether or not to save for retirement, take a trip home to visit family, or go to college. Members are taught to reduce most decisions into two oversimplified choices; usually these choices are in this format: you can either do "A" and go to hell, or you can forego "A" and be saved/be happy/be reincarnated/whatever. Of course, you've still got to be able to say that they weren't pressured into making the decision the leader wanted them to make, so the words "it's your choice" are often said at least once. Here are some examples:
Should I save for retirement? - "Well, you know, brother, Jesus said we weren't supposed to lay up treasures on Earth, and the church really needs the money, so saving money for yourself would be mighty selfish, now wouldn't it? But, it's your money, so you do what you want with it. After all, you're the one that will have to answer to God for it, not me."
Should I go to college? - "I know you would like to get an education, but you know how God hates pride. I think if you look deep down in your heart, you'll have to admit that you only want to get a degree because other people will admire you. That's wrong; I know it, and you know it. But, hey, it's your choice!"
Should I take that job? - "Well, you know this will keep you out of church on Wednesdays. God just won't be able to use you as much as he could. I know your family needs the money, but maybe you should just trust in God and hold on a bit longer until a better job comes along." A "better job," of course, is one that doesn't interfere with church in any significant way.
There is another aspect of black-and-white thinking: the denial of human nature. No one is all good or all evil, yet scriptures such as "Doth a fountain send forth at the same place sweet water and bitter?" are often used to make the cult's case that a person is all good or all evil (as needed, of course). For example:
They can't possibly have done that because... - "Now, sister, I'm surprised that you'd say that Pastor 'X' raped you, because he's a good man. I mean, I've seem him invite the poor to stay in his own house, and you've got to admit that his messages are inspired by God. Would God continue to bless him so powerfully if he went around raping people? Of course not. So you just need to admit that you're making this all up..."
You shouldn't listen to/associate with them because... - "I know you were good friends with Al and Dee, but you know that they've forsaken God's calling on their lives. You know how Satan deceives people when they walk away - especially those two; they were always so deceitful - so you just make sure you don't associate with them or you'll end up lost too. After all, everything they're going to tell you is nothing but a pack of lies." This type of reasoning is sometimes called "poisoning the well."