There is some debate over just how despised and hated atheists really are in America. Surveys reveal more distrust and animus towards atheists than towards almost any other group, but at the same time atheists don't appear to be routinely victimized by hate crimes. Given the ambiguous nature of "hate" and "animus," we'll never have a truly objective and scientific test but we can look at behavioral indicators. One such test is how willing people are to believe outrageous lies about atheists.
Elizabeth Anderson wrote the following about the malicious falsehoods said about feminism and feminists:
Here's a measure of how much a group is despised: how much malicious absurdity can one ascribe to its members and still be taken as a credible source on what they say and do? With respect to feminists, the answer is quite a lot.
We can say something similar about most groups that are targets of bigotry and discrimination, including atheists. No matter how absurd an accusation about atheists is, it's always possible for Christians to say something even worse. Currently the most absurd I've heard is that atheists can be "wackos" who "want your children to grow up and marry trees." I don't think it's possible to even parody people who actively believe and spread such utterly ridiculous accusations.
What's important here, though, is the fact that people accept such claims without objection or criticism when they involve a despised group but would never do so about other groups. The more hated a group is, the more outrageous a claim can be and still be accepted — and the source will still be treated as credible. There are two reasons for this: first, they want these claims to be true regardless of how horrible or outlandish they are and, second, they want to see harm come to those about whom the accusations are being made.
Immorality of Beliefs
Accepting and spreading negative beliefs about a group harms members of that group. At the very least they may become mistrusted and thus prevented from forming the same business or personal relationships as others. In more extreme cases, the harm might include actual violence. When those beliefs are accurate, the resulting harm may be just. When those beliefs are false, however, the harm can in no way be appropriate or just. In both cases, no one who spreads such accusations can protest that they don't do so with the intent that those targeted suffer as a result.
The unfortunate conclusion before us, then, is that people who accept and spread outlandish, absurd accusations about a despised minority like atheists, gays, feminists, or Muslims are actively seeking to have members of that group harmed in unjust ways. A moral person does not believe negative, hateful things about others and especially an entire class of people without very good reason. Simply wanting those claims to be true, though, doesn't qualify as a good reason.
A moral person doesn't believe rumors that their neighbor is a child molester or a Muslim terrorist without good evidence and doesn't spread that rumor in the absence of any evidence unless they want to see harm come to their neighbor. The same is even more true when we are talking about groups which already experience discrimination.
People who claim, without good evidence, that blacks are naturally inclined towards crime, that Jews are greedy, or that atheists lack any basis for contributing to moral debates, necessarily want members of those groups to suffer unjust and unnecessary harm. They are hate mongers who want nothing more or less than to hurt other human beings simply because they are different.
Falsehoods as Oppression
To put it another way, there are Christians out there who believe and spread outlandish and absurd accusations about atheists without good reasons and who must, as a consequence, want atheists to be harmed through the widespread acceptance of those accusations. These Christians want you to be harmed and to suffer unjustly for no other reason than because you are different from them. They want to worst to be true about you and want your life to be unfairly worse as a consequence.
The widespread acceptance of false beliefs about atheists thus isn't simply a series of mistakes that can be corrected by explaining the truth. People who are honestly mistaken appreciate learning correct information, but haven't you ever noticed how defensive Christians get when their misconceptions about atheism are corrected — even if just about the definition of atheism? This is because they want and need to believe these falsehoods in order to further their ideology of oppression. The harm caused to atheists can't continue if the truth about atheists becomes generally accepted.
The outrageous lies which Christians spread about atheism are thus an integral and necessary component of your oppression. The same is also true about the outrageous lies which are spread about gays, women, blacks, immigrants, and every other minority which suffers at the hands of bigots in society. Ending oppression means stopping the easy acceptance of lies about us and that requires far more than simply providing people with the correct information.
Since most of these people are probably not otherwise so immoral in their lives, a first step has to be to get them to understand how much harm they are actively promoting when they accept and spread falsehoods about others. We need to get them to look a bit more closely in the mirror and fully appreciate what they are doing and what sort of person they become when they do it. Then, hopefully, they will be prepared to accept the truth over lies and stand against bigotry rather than for it.