I don't know how it works for everyone, but that was never my experience.
Realizing and embracing my atheism was wonderful.
What makes me "angry" are the believers forcing their beliefs on everyone else.
That straight-up pisses me off.
I think, in some cases, what gets perceived as "atheist anger", is actually
the pushback against being told how to live. The believers have been having their
way for so long, they perceive anyone having the temerity to question them as
discrimination. Hence, their persecution complex.

The realization that I am atheist was liberating. Nothing there to grieve or be angry about.

The source of my anger is all about seeing the different types of damage that religion has done and continues to do, while simultaneously feigning righteousness. The manipulation of the indoctrinated. The failure of the U.S. to maintain the separation of church and state. The denial of knowledge and the discouragement of the quest for knowledge. The various ways that religion slows the progress of humanity toward reaching our potential -- whatever that might mean.

That is what my anger toward religion looks like.

The path has been easier for me than for many because before recently becoming Atheist, I was a long time Agnostic who never wasted too much time with religion. So I can understand anger about having expended so many years on nonsense. And we all are continually fighting against the tide of those trying to shove such ideas back down our throats. And though I would never want to take back the many hours I spent studying the various arguments that led to my acquiring all the knowledge I am now armed with that allowed me to transition from Agnosticism to Atheism, I do sometimes resent that all of it was even necessary in the first place.

I was 17, a junior at St. Joseph's Prep in Philly, whenthe Jesuits mad a fatal mistake. Instead of shoving "God's Word" down my throat with a feeding tube, as had been done for 11 years, they said, "This is what we believe. What do you think?"
Well, the notion that we were allowed to THINK about any of this was revelatory. And once I applied rational thought to this absurd back-story, God vanished in a puff of logic.
I knew that my abandonment of Christian mythology would not be taken well by my Irish Catholic parents. But nothing could have prepared me for my mother's response. She said that she hoped that in the course of my life, a tragedy would befall me that would bring me back to Christ.
What might that look like? Cancer? The death of my child? It was in that moment that my view of religion went from mocking an obvious, ludicrous fairy tale, to an understanding of the pernicious and malicious manipulation of the minds and hearts of the flock. My mother, a good and kind and loving woman, would see her son suffer, or her grandchild die, if that's what it took to bring me back to God.
So yes, I suppose I am angry at religion. From the countless deaths brought about in whatever name you've given your god, to the hurtful words of a deluded mother, I join with John Lennon, and imagine there's no religion.

I'm not angry for being raised a Catholic. I'm actually grateful. It gave me an insiders understanding of religion that I wouldn't have otherwise, especially of the comfort that traditions and repitive prayers bring to many. After I'd left religion behind, I read the bible, the gnostic ghospels, and other texts that just confirmed what I already knew. That religion is a political beast used to brainwash and control the masses.

I get angry when I see the damage or terrible hypocracy that religion bring about. Most of the time I treat religion as silly nonsense not worthy of any respect beyond that of common fairy tales. But when I see the bullshit that religion does to people and society as a whole, I have every right to be upset when there is clear and present damage due to its influence.

I agree with both comments. I had a relatively short period where I was very angry. One of the reasons was that I was a minister for twenty plus years and I felt angry that I had wasted my life on something that is meaningless, that I had given so much and had sacrificed my family on the altar of ministry and yet I didn't receive the benefits of that. I guess I was going to experience them in the next life haha.

What I am angry with these days is the hypocrisy, the fact that people consider Christians to be more moral than atheists even though the statistics show otherwise, the history of the church and all the damage it has done to humanity and the planet, and the deception that continues by church leadership.

I am angry at the Catholic Church for the damage it did to me, to my mom, to many defenseless children, and to millions of others over the centuries. However, that is not tied to my concluding that there is no evidence for a god.

To me, it's the theists' way of saying "outspoken" atheists. Theist rather have "don't ask, don't tell" so we don't threaten their faith.

So many have been seriously hurt by religious beliefs being shoved on them since childhood. For one thing it has prevented them from evolving their own identity and being "me" is fundamental to living. Those who are gay or different in any way are particularly vulnerable. The point is religion has hurt them and overcoming this was never easy. Most have had to pay a heavy price for this freedom.

That could mean different things to different atheists of course. I get upset when I think about all those beautiful Sunday mornings and often nights as a kid..and prayer nights on Wednesdays..that I wanted to be outside instead tossing a ball..or sitting at home playing guitar instead of being stuck inside that Baptists church. If others get comfort from having an invisible friend that protects them and listens to them..saves them from their sins..it's fine with me. I don't get angry. Whatever works to help them get through it all.

People have a right to choose to be deluded. What makes me angry is how religious leaders knowingly lie to and use people to enhance their power and wealth, and how they try to impose their dogma on others.

For everyone there are processes.

As a recovering catholic, yup...I was pissed off.

I don’t think the angry atheists “convert” to a secular science informed viewpoint that you referenced. Having some indignation for the wrongs perpetrated by religion and viewing the world from a science and secular informed rationale are not mutually exclusive. Do you?

I grew up "Christian" but it was never really a big deal. It was just the cultural norm. I occasionally went to Sunday school at the Nazarine Church but my parents never did. Because it was never that important in our home I don't feel any of the anger that I might have felt if I had been subject to opressive dogma. I do think that our public school system is so deficient that we should all be a bit pissed off. I know teachers get indignant that they aren't held in higher esteem, but most of them aren't really that great and don't care that much about students.

Hell yes. 12 years of Catholic school. I realized In undergrad how sorely my math and science education had been compromised in favor of mythical BS. That’s why I went into music and later law. At least I could still read.

I'm not sure about the stages of grief. It's likely true for some. I think there are many people that have become bitter and cynical about religion because they feel they have essentially been lied to all their lives.

Greta Christina has written a book on a hundred reasons why she, as an atheist, gets angry. Here's a flavor of that in a presentation she gave:

Good insightful question.

Probably the newer atheists are more angry. I've noticed with 2 people on here, that they are new. They have anger at religions. I did too, a year ago.