What are you atheists so angry about?
This common perception about atheists is particularly unfortunate because, I am sad to say, it is so often true. Yes, there are quite a few atheists out there who are angry but to address the question, what are they so angry about? Being angry is not in and of itself bad if you have just cause for your anger.
There are many things which can cause atheists to be angry. Some were raised in very religious homes and, over time, they came to discover the things they were taught by family and clergy were all wrong. People don't like to have the sense that they were deceived by those in a position of trust and authority, so this can result in anger.
Some atheists come to view religion or even just theism as being deceptive and, hence, harmful to society. Any atheist who has the best interests of society at heart will be bothered by belief systems which they honestly consider misleading. The influence of such beliefs can then cause some to become angry.
Still other atheists experience ongoing discrimination because of their disbelief in gods. They have to hide their atheism from family, friends and coworkers. They don't know any atheists except those online. They have to listen to others make disparaging comments about disbelief without being able to respond. This kind of pressure isn't healthy, psychologically or emotionally, and can readily lead to a person becoming angry.
However, it isn't true that all atheists are angry. Even among those who have gone through the above experiences, many aren't angry or, at the very least, are no longer angry. As for those who are angry about some things, whether their anger is justifiable or not, most aren't angry all the time or even every time the subject of religion comes up. Many atheists are quite happy and don't lash out at religion or theism. Thus, idea that all atheists are angry is an over-generalization at the very least.
Why do some people ask the above question and assume that atheists as a group are angry? One reason is the obvious: there are enough angry atheists, especially online, one can honestly get the impression that this is how atheists normally are. This is, however, a bit like assuming that all Christians reason very poorly and know nothing at all about logic or critical thinking an impression which many atheists get after dealing many such Christians online.
There is, however, the additional implication that if atheists are all angry, then this somehow undermines or invalidates the atheist position. That simply isn't true, and to suggest that it might be amounts to little more than an ad hominem argument. Even if all atheists were indeed very angry about religion and/or theism, that wouldn't mean that theism is reasonable or atheism unreasonable. Most Jews are angry when it comes to Nazism, but does that mean that Judaism is invalid? Many blacks in America are angry about racism, but does this mean that the Civil Rights movement is invalid?
When it comes to debates about which is more reasonable, atheism or theism, the question about atheists being angry is ultimately irrelevant. The only thing which would make it relevant is if the questioner is honestly interested in improving the relationship between atheists and theists. Unfortunately, this seems to be rarely if every the case. In my experiences, theists bring this up as a means for subtly attacking atheism, putting atheists on the defensive about themselves and others. Never do I hear such a person sincerely asking if atheists might have any reasonable complaints about how they are treated and therefore perhaps sound justifications for experiencing anger.