This grates me as well; the notion that "they became so angry at God, they rejected him altogether". But I guess saying that religion and faith is a 'crutch' is just as grating to those who believe.
I think we talk 'across' each other, because we live in "different universes". Believers live in a universe where God exists as a fact; atheists live in a universe where a god either does not exist at all, or is very good at hiding. Atheists don't go "Oh, I know there's a God, I just decide not to acknowledge his existence, 'cause I'm so mad at him". It just doesn't work that way.
Do most people who leave the JWs lose faith altogether? Perhaps, I don't have the numbers. Is it because they became 'angry at God'? I don't think so, in most cases.
Why would many ex-JWs become atheists simply because JWs were wrong?
Well, there is of course the matter of praying to Jehovah and actually believing in him and then finding out it's not true, but aside from that, I'd think most people would then try to find out where God actually is and not reject a God altogether.
But - JWs are a very strict, cult-like organization. When people are set free, they are more likely to wish to find answers from the other side of the argument. They've already heard the creationist side. Now they want to look into the evolution side. They've heard the Bible apologetic side (prophecies come true, inerrancy, etc.), now they'd like to research the other viewpoints.
For me, when I saw how the Watchtower mis-quoted scientists to bend their statements into looking like they supported the JW view, I wanted to look into what scientists actually said. I still wasn't ready to accept evolution, so I went to sites like Answers in Genesis etc. at first, when science said things I didn't want to believe. After a while though, I found that other creationist sources were no better than the WT. They lie, distort, misunderstand, misrepresent, etc. etc. in an effort to find 'evidence' of special creation (and regularly also of a global flood).
I found that properly understood, evolutionary theory makes sense. That in itself does not preclude a Creator though, but it was a starting point, and it does preclude a literal reading of Genesis. I then looked into the Bible.
Since creationist apologists had been so dishonest in their arguments, I decided to look into the Bible from a critical, skeptical point of view as well (having been brought up on the apologist side). And I found that you can't call the Bible the inerrant word of God unless you distort and twist it in a way that would make Lord of the Rings become a literal fact of history as well if treated the same way. Sure, the Bible has some actual historical parts in it, some nice poetry, some good advice etc., but that's pretty much it.
I looked into cosmology, geology, anthropology, archeology, biology (have a lot more to read, though!), and found explanations that were natural for the things we see in the universe. I also found that there was room for not having the answers at this point. That further study could reveal it, and it wouldn't be the end of the world not to know right now. As a JW you have "all the answers" (or so they think).
Meanwhile, God got less and less to do. Eventually he was all but out of work as I saw it. He could still exist by all means, but it would have to be outside of our universe, and in a capacity that - when combined with my own personal experience - did not directly affect us humans. That's deism though, and pretty much any God mankind have prayed to could fit the bill (if that God had stopped responding some time ago). What God should one choose?
I looked into logic; arguments for and against God. Or rather; for and against a personal, interfering, all present God.
Combined with my own personal spiritual experience (or lack thereof), I came to the conclusion that without further proof, I could not believe in God, and especially not a specific God of any of the religions.
Can it change?
Sure - I'm open for it. Some Christians - on this forum there are a few of them - has simply decided to treat those Biblical passages and books that go against modern scientific discoveries as poetry, allegory, non-literal stories to tell an underlying point. Or; once true, but exaggerated and blown out of proportion over time. That God's Word is still in there somewhere. I guess I could do the same.
There's just a strangeness to this God who has done little else than perhaps start it all, and who - when deciding to speak to mankind - decides to let fallible men write down his words, but in a way that - if you critically look at the sources - makes it a big jigsaw puzzle with the pieces jumbled around and put together again carefully by other men in an effort to make it all fit together, but ultimately becoming a little jumbled anyway, and ripe for misunderstandings and various interpretations.
I see an awe inspiring greatness in nature, in life, in music and in love that perhaps some would collectively call 'God', but I don't see the personal Creator God of the Bible or any religion at this point.
And it's not because I'm angry with God.