Why does God make you believe that he has stabbed you in the back? The answer is so that:

You will be unable to refrain from cursing him.

But why would God want you to curse him? So that you see that:

Your confidence, courage, and boldness continue while you are cursing him.

What is the purpose of that? So that you see that:

Your confidence, courage, and boldness are not dependent on your belief in the goodness of God and/or on your faith in God and/or on any persuasion that results from those two things. And that you see that your confidence, courage, and boldness are infused into your soul (psyche) by God (the Holy Spirit of God) himself.

Why is that knowledge important? So that you see that:

You don’t need proof of anything to have confidence, courage, and boldness; specifically, proof of the existence of God, proof that God is good, proof that God is managing your life, proof that the Bible is the Word of God (collection of messages from God), proof that the King James Bible is the Word of God (collection of messages of God), proof of what is the will of God for you, and proofs of other things.

Why do you need to know all of that?

So that you spend less of your life seeking the proofs mentioned above and more of your life doing the good that God wants you to do.