Some of these reasons are insulting.
1. Their father was abusive or absent in their childhood.
My father was not abusive, but he did die when I was only 9 years old. However, anyone who thinks that had anything at all to do with me rejecting the Biblical God is jumping to totally false and incorrect conclusions. My father's early death had absolutely nothing at all to do with me rejecting that Abrahamic religions.
2. They are disappointed how God has acted, or failed to act, in some situation.
Which "God" are they talking about? The God described by the Bible?
In that case, yes I most certainly would be disappointed and even insulted by the God portrayed in the Bible. IMHO, the God portrayed in the Bible is an immoral idiot. Absolutely. And that is a good reason for rejecting a religious dogma. Especially if we are being asked to believe it as a matter of faith.
Why would I want to have faith that I was created by an immoral idiot?
So yes, that's a good reason to reject the Abrahamic religions.
3. A spirit or vision or flashing insight has told them there is no God.
Actually I'm not an atheist in the absolute sense. I actually believe that there there may very well be a God. But it's definitely not the God depicted by the Hebrew Bible.
4. A "No-God" universe obviates the need for moral behaviour.
Yes, this is yet another insult because it implies that I don't have moral values.
As I just said above, I don't actually believe in a "No-God" universe anyway. But even if I did I would still have higher moral values that have been attributed to the Biblical God. After all a large part of the reason that I reject that portrait of God is precisely because it is an immoral as well as a stupid picture of a God. So even if I was a pure secular materialist I would still have moral values just because it's what I personally desire. Contrary to what Christianity demands I might add.
My reason for rejecting the biblical picture of God is quite simple and straight-forward.
The biblical picture of a God simply makes no sense. It's not intelligent. It's not moral. And it's not wise. It's just a history of a highly immoral and male-chauvinistic society that used religious bigotry and fear to try to control the masses. And unfortunately it has succeeded so powerfully that it continues to coast along on its own momentum to this very day.
I will give the creators of the Abrahamic religions credit for one thing. They sure are good at creating religions that brainwashing people to actually keep the cult going.
If I'm angry about these religions I'm not angry with their false gods. That would be silly. But instead I'm angry with the people who contributed to these religions over the centuries and with the proselytizers of these religions that continue to propagate them and support them to this very day.
I see these religions as a very serious cancer on humanity. They are bringing us down folks. Bigotry under any guise is still bigotry and religious bigotries are not exempt. Religious bigotry is still bigotry.
So I not only don't believe in the Abrahamic religions making me an Abrahamic Atheist, but I am also dead set against them, making me an Abrahamic Anti-Theist.
I seriously believe we would be far better off without them.