The Bible Teach book uses the example of a math teacher who is challenged by a student who disagrees on how to resolve a math problem. The teacher then lets him attempt to prove his point knowing that he can only fail. The object of the exercise is to show the rest of the students that the teacher is right - that there is only one way to resolve the math problem....This is likened to Jehovah letting Satan exercise his power over the world so that the entire universe can witness his failure and that only Jehovah's ways lead to happiness...
Instead of maths, what if the teacher taught chemistry and a student would want to prove that the teacher is wrong when he says that certains chemicals can't be mixed without causing an explosion that would wipeout the school...would any sane, responsible, loving teacher allow such a student to experiment and wipeout the whole class just so the teacher can prove he was right? Isn't this what Jehovah is doing? Letting billions of people suffer and die just to prove to the angels that he is right. Who else is he proving something to? Surely no one on earth since no one is aware of this sovereignty challenge taking place in heaven....except of course for the JWs.
In the same chapter you can read that Jehovah does not intervene to prevent evil because it would make things look like Satan is right and that this old system is succeeding and he would be supporting the lie. So dad has several sons and he tells them to stay away from the river bank because they could fall in and drown. The oldest son tells his 5 year old brother that it is safe to play by the river, that he won't drown...and the boy falls in. What kind of a father would let the boy drown just to prove to all his other sons that he was right. Or what king of a father would refuse to save the boy because it would make it seem like the older son was right in telling the boy that he wouldn't drown....
It is so strange that I read this several times without ever clueing in on the insanity of such reasoning...and now I can clearly see the deceptive reasoning used by the WT.