I don't know that anti-theists and atheists are necessarily determined by how much they've been persecuted by the religious so much as anti-theists are still in that angry "religion is a house of cards, and people have been trying to forcefeed it to me and control me with it all my life" state.
Personally, I came to the conclusion that I wasn't religious after enduring confirmation (a Lutheran practice of being educated in the faith leading up to your first communion). Every Wednesday for three years I went to church, recited some tenet of faith I'd memorized over the previous week (such as the Ten Commandments, a Creed, or bits of the Lutheran Catechism), then did bible study with my Pastor and other people undergoing confirmation. I never had an emotional experience at church the way most people do, so all throughout the process I expected that I'd have some sort of spiritual awakening--it never happened.
Especially towards the end, I started to get very nervous because the Pastor (who I trusted very much) told us that to partake of communion without the right feelings in your heart meant damnation. I began to doubt whether I actually believed in anything at all, but I went through it with it, got confirmed, and it was over. It wasn't until after that I realized that I truly had no religious inclinations at all and never had; anything I felt or believed before was simply transplanted into my mind and predicated on the trust I had for the people who'd made the claims to begin with. Then I got very angry.
If you're raised in a Christian household, in a largely-Christian country you don't realize that there are other legitimate viewpoints on religion (aside from other Christian denominations), and that works right into the hands of the pastors and parents throughout the country who are looking to implant their beliefs into children (though admittedly they have good intentions). It's horrifying to wake up and realize everything you've been told for the first fifteen years of your life was just an opinion with little basis, not the invincible, solid fact that it'd been passed off to be by friends, family, and other trusted individuals.
So I was an angry, militant "god doesn't exist" Atheist for a time. I loved debating with the religious, I liked to insult them, and of course I loved the "religion is an opiate for the masses" type quotes. I think most Atheists go through a similar phase, but I hope that they, like me, eventually dig themselves free from the emotional baggage and try to be the better person by simply admitting that they do not know when it comes to religious questions. I think "I do not know" is the only way you can be absolutely certain of any religious position, which is why I pride myself on Agnosticism.
Sure, there are still things that get on my nerves. I hate it when people try to justify with reason their religious beliefs, marginalizing the role of faith in the process, but it doesn't bother me that they believe what they do, just how they seem to think that it's reason-based. Absolute, blind certainty, I think, is very dangerous as well. Sure, it can lead people to do great things, but it can also lead to horrific outcomes just as easily. And of course my final pet peeve is religious people who want to impose their theology on others by force (attempting conversion isn't so bad if it's not backed up by anything in my view) or automatically look down on people who are not religious.
I'm irritated by the fact that we still live in a society that supports and cultivates religious views in official institutions. Separation of Church and state isn't going so well this day and age. Furthermore, I wish the majority of religious people understood that morality does not come from religion (and therefore non-religious people can still be moral).
All of my gripes and observations aside, I think it's going a bit far to say the world would be better without religion. The fact of the matter is, any philosophy (and I believe religions fall underneath this umbrella, just they're a philosophy that isn't governed by reason) can be taken to its extremes and used to justify violence, hatred, and ignorance. Anti-theists love to point out all of the bad things that religion has done, but they forget the good. And while it's true that the "good things religion has done" are actually "good things that people do," religion often provides the framework, the motivation, or the basis of that.
The only things I'd like to see amongst the religious are less certainty, less extremism, and less bias.
EDIT: Afterthought, damn that's long, I wonder if anyone's actually going to read this. I'm not even sure how relevant it is, given how personal parts are. Heh, sorry.