Question: When atheists explain why they became atheists, what atheism is, and what atheism is not, religious theists (and especially Christians) often refuse to accept what they hear. This happens even when atheists just answer a specific question which they were asked. Why do theists behave this way? What can I do about it?
Response: Most atheists who have had discussions with religious theists, especially Christians, about religion, theism, and atheism have probably experienced this. The atheist explains something about their own atheism (like why they became an atheist) or about atheism generally (like what atheism is) and the religious theist refuses to believe them. Even if the theist asked a direct question and is receiving a direct answer, they act as though they already knew the answer and dismiss what the atheist says.
Typically, the religious theist claims that the atheist is somehow "in denial" about the truth. They didn't really become an atheist because they realized that the arguments for the existence for gods were flawed, they became an atheist because they wanted to live immoral lives without having to be answerable to God. Atheism isn't really just the lack of belief in gods, it's an anti-God, anti-Christian religious ideology dedicated to the eradication of religious liberty and the imposition of a secular, socialist dictatorship.
These beliefs held by the religious theist have little or nothing to do with reality, but they are announced with great conviction and sincerity. No matter what the atheist says or does, it will appear to have little impact — the theist will remain convinced of whatever they believed from the outset, and contact with a real atheist who reflects none of these things is not seen as any reason to reconsider. Given all this, why did the theist ask any questions in the first place? Why ask questions when you are convinced you already know the answer and will not be swayed by any contrary answers, evidence, or arguments you might hear?
The answer, I think, is that Christians asking such questions aren't asking real questions at all. A real question is an admission of ignorance, an expression of a desire to learn more, and an invitation for someone to help a person expand their knowledge, understanding, and horizons. People can only ask genuine questions on the premise that there are things they should or could know which they don't already know, that they might be mistaken about some of the things they think they know, and that one might need to change in the future. Given these conditions, how often do Christians ask genuine questions of atheists? Not very often, in my experience.
Instead, it's more common for Christians to only ask rhetorical questions about atheism and atheists. They are like parents asking their children what happened to the missing cookie: the parents know very well what happened and are only interested in seeing if their children will own up to what they did. Atheists who admit to being hateful and in denial about God are children who have done wrong, but can be redeemed because they acknowledge their sins. Atheists who refuse to admit this are twice damned: not only do they hate and deny God, but they refuse to even be honest enough to admit what they have done.
Of course, many of the questions people ask in their daily lives don't quite fall into either extreme. It's common for us to neither be absolutely convinced of the answer in advance nor 100% open to new and exciting information from the person before us. We all have assumptions and biases which cause us, quite unconsciously I think, to form opinions in advance about what sorts of answers we will receive from many of our questions. We may not know why a politician is advocating a particular policy, but long before we get a response to our question we may be suspicious that influence from lobbyists, racism, indifference to the poor, or other unsavory sources are involved.
Even so, how often do we voice our suspicions or denials to the person who just answered our question? Even when we have strong suspicions, we are unlikely to say so right away; instead, we generally take what is said to us at face value. Hardly anyone ever tries to start an argument by claiming that the answer is just a lie designed to cover up one's denial of reality. If we say anything, it will be to someone else later on where we quietly voice our reservations, suspicions, and concerns.
For some reason, though, such basic courtesy and respect tend to be lacking when it comes to how Christians treat atheists. A Christian who would never say to a person "you didn't marry him for love, you married him for his money!" has no qualms with saying "you didn't leave Christianity because you were persuaded by stronger arguments for atheism, you left because you had bad experiences with a bad church!" (or some other excuse). How many of these same Christians will be found in other situations claiming that atheists are the ones who are rude, disrespectful, and intolerant?
Most atheists probably don't mind answering genuine questions about their atheism or about atheism generally, but they also probably aren't the least interested in faux questions from someone who arrogantly presumes to already know the answers. If they were completely honest, they wouldn't ask "why are you an atheist?" but simply say "I don't know you, have never met with you, have never spoken with you, don't know any of your friends or family, and didn't even know of your existence until 10 minutes ago, but I know exactly why you are an atheist."
Put that way, of course, it's an absurd position to adopt and those who are inclined to try should stop themselves before they get that far. Atheists who encounter it should refuse to play their game. Rephrase their rhetorical question into the declarative assertion that it really is and make the theist support what they are saying. The chances of them coming up with anything reasonable are so small that you're practically guaranteed a quick end to a conversation that was never going to go anywhere productive anyway.