My answer to the Askville question "
If atheist believe in free speech, why do they slander Christians?" I've been discussing this a lot, of course, so my apologies that most of this isn't new.
Maybe I should write a book about the whole topic of atheism. What do you think?
I'm afraid that the question, as asked, doesn't quite make sense. Let me deconstruct it, and then I will try to give an answer.
1. Not all atheists necessarily believe in free speech. Atheists are not a uniform body. They share one point in common: they do not believe in the existence of any god or supernatural entity (and there are probably some self-described atheists who DO believe in some sort of supernatural being, although I can't see the sense in that myself). Apart from that, there are Republican atheists, Democratic atheists, Communist atheists, Libertarian atheists, neo-con atheists, socialist atheists...atheists who like chocolate ice cream...atheists who like vanilla ice cream...atheists with diabetes...pretty much the entire human spectrum of experience and thought is represented in the atheist community (with the obvious exception of theism, of course).
So while I hope that most atheists believe in free speech, I'm sure that some don't.
2. Belief in free speech does not preclude slander. In fact, it would be closer to say that the reverse is true; that free speech must, by definition, allow for the possibility of slander. In any case, this is very much an "apples vs. oranges" point. Free speech and slander are neither opposed nor interchangeable.
3. Suggesting that Christian belief is delusional or not based on demonstrable evidence is not "slander". Slander has a specific meaning: "In law, defamation (also called vilification, slander, and libel) is the communication of a statement that makes a false claim, expressively stated or implied to be factual, that may harm the reputation of an individual, business, product, group, government or nation." (Wikipedia)
For such statements to be slander, they would have to be shown to be false. Since no one has irrefutably proven the existence of ANY supernatural being or force (much less the Christian God) no case for slander can be made.
It could also be argued that atheist arguments that Christianity is not based in fact do not harm anyone's reputation, since the vast majority of the American public is putatively Christian. Are they going to believe a fellow Christian, or the statements of a godless, immoral atheist - statements which impugn their own Christian belief just as much?
I'm afraid that simply disagreeing with Christian belief, annoying and frustrating as it undoubtedly is, is not in itself, slander. It's simply disagreeing. Yes, some atheists insult Christians, sometimes gratuitously; as an atheist myself, I regret that they do. But that's hardly a vice restricted to atheists. I've seen far more hatred and insults directed by so-called Christians towards atheists! Probably because there are so many more Christians than atheists.
You'll also see just as many - no, far more - insults being hurled around online and in the real world over politics, sports, and virtually any other topic on which two or more opinions exist.
I have seen a growing tendency in some Christians to claim that any disagreement with their belief, any expression of disbelief in theism, is somehow a brutal attack on Christianity. It is a common truism among some extremist American Christians that Christians are a persecuted people. This completely overlooks the fact that Christians rule America, rule atheists, and have since the founding of the Republic.
Every President has been a Christian, or at least a nominal Christian Deist. Every Senator has been Christian or Jewish. Virtually every Representative and state governor has been too. And it's not as if their faith isn't relevant; every single one of them has loudly proclaimed their religious devotion. This despite the fact that the Constitution mandates that "...no religious test shall ever be required as a qualification to any office or public trust under the United States"! (Article VI, Section 3)
Meanwhile, atheists have lost jobs for not being Christian. They have had their cars keyed, tires slashed, and their children have faced ostracism and death threats in school - all for the "crime" of not being Christian. And (perhaps worse) for the crime of not shutting up, keeping their heads down, and quietly accepting extremist-Christian-inspired efforts by the government (the Christian government) to infringe on the basic protections afforded to all Americans by the First Amendment. Atheists in our schools and our military face real persecution and discrimination daily for their unbelief...and Christians claim to be persecuted in this country?
That's an insult to Christians and other theists around the world who really DO face persecution - and rape, torture, and murder - for their faith. At the hands of governments in the Middle East and China, for example.
I really am sorry that you feel attacked by the statements of atheists. And I regret any instances where you've been insulted or flamed by atheists; I think that such attacks are not only unproductive, but are actually harmful to the whole idea of inter-faith dialog. I've counseled atheists (and Christians) to try to avoid that approach, because all it does is hurt your own argument.
Having been on the receiving end of such flames (on all sorts of topics) I know how much they hurt. I'm an old Usenet veteran, so I've been called every name in the book. Heck, I was once called "an annoying little a--hole" in a nationally-distributed magazine. Now that was slander! I'm nearly six feet tall, and used to be a defensive tackle - no one has ever called me "little" to my face. 
I still get a little angry when I think about that, to tell you the truth. But what I've learned is that is someone starts flaming you, it's a sign that they've run out of other things to say. The secret is to respond reasonably, and let the flames roll off your back - a lesson that I'm still learning.