The same reason that unlike most live and let live believers, some Christians (or Muslims or whatever) plead with,scream at, kill and launch crusades against people who refuse to subscribe to their conviction in religion A, B or C. For some people believing in something and expressing it just isn't enough unless everybody else believes it too. I have come across many atheists who believe that religion is a negative force which has caused great harm in the world (based on evidence of centuries of religious wars I'm inclined to see their point - can anyone think of a major war or conflict where religion WASN'T involved in some way or another? Don't rate me down for that comment, I'm genuinely wondering, because I can't- as far as I know no-one has yet launched an "atheist" crusade, but I'm sure its only a matter of time!) and therefore consider it their moral duty in the interests of improving the future prospects of the human race to debunk the "hoax" (or whatever they might call it) whenever given the oppurtunity, in much the same way as an Evangelist Christian (for example) considers it their duty to contribute to the salvation of as many souls as possible by spreading the word of God. Same attitude, different beliefs. (Before anyone say anything, I'm not saying this is the right attitude, just explaining some reasons why it might exist)

As an agnostic, I find that atheists or those of my own stripe, tend to take that route only when a christian fundamentalist is trying to shove their belief upon us. I've never encountered an atheist or agnostic who does the "screaming" first. It's usually the believers who start it all when they see something they don't like. I agree whole heartedly with Lady Fushia in her post. What totally befuddles me, is that agnostics are on the fence, but sometimes labelled as atheists by fundamentalists, just because we want to THINK about it. They scream at me...I'm duty bound by my own conscience to defend my thoughts ( as they are). Atheists or Agnostics as a whole, I find to be thinkers that weigh both sides of the argument of the existence of any God. I know I'm going to be rated down by this. It always seems to happen when one posts a personal opinion that a verbal opposing group detests. I also know I'll get a bagful of scripture to boot, which just might prove my point.

I agree with both answers already submitted but would add that the question suggests that atheism is a "personal belief". It is not. It is the absence of belief. If an atheist has an issue with believers it is not that he believes something different to them, it is that they base their actions on belief whereas he bases his actions on evidence.

Why would he? Because he's rude and wants attention. His actions have little to do with his personal beliefs or opinions. It took a while to understand - no big surprise there - and the core issue here isn't WHAT he rants about; it's WHY he does it at all. If he was a believer, he would act the same way, exhorting the opposite of what he's wanking about now. I probably should have asked this in the "Manners" category (if there is one) or maybe "Mental Health". My apologies to anyone who felt the question was offensive. No disrespect intended.

Well, I'm not an Atheist; however, if I were I would respect the beliefs of others. I do struggle with the issue sometimes. As a Wiccan, I still consider it sometimes, even though it is against our beliefs. The reason? The actions that are taken as a result of strong religious belief, particularly of the monotheistic type. Why take care of the environment if God is going to come and take care of all of that? Why negotiate a peace deal for a two-state solution when God has promised the land to YOU (Jews and Muslims)? Large numbers of voting blocks in the US motivated by religious fervor scare me. These blocks want to impose their moral beliefs on the rest of us. The numbers of them are making a difference in our daily lives, and in the laws of this country. This type of fervor does not understand compromise or pragmatism. (Sometimes it doesn't even understand documented history.) So, I'm not an Atheist, and I've never tried to talk someone out of his/her personal religious beliefs; however, I can and do understand why some would. (Which is not to say that I agree with it, but I completely understand the temptation.)

Personally, I have never seen or heard an atheist do this. In my own life, I would go as far as attempting to have a rational, philosophical discourse about the different beliefs I hold from another peson, I would never scream, yell, plead, or in any way attempt to force my beliefs (non-beliefs) on someone else. I realized a long time ago that not only is this rude and hypocritical, it's also completely pointless. There's virtually no chance a firm believer in religion is going to hear what I have to say and respond with "Wow, I've never thought of it that way before. You are so right, I've been wasting my life believing in all this stuff!" For the record, I do believe in God, or at least some kind of supreme force. It isn't necessarily the Judeo-Christian God, it is my own concept. The problem I have with so-called "believers" is not with them personally, it is with organized religion in general. Everyone should be free to discover and believe in God in their own personal way, not the way some guy with a funny hat tells you to.

Because they are an extremist atheist, just like you have extremist Christians, Baptists, Muslims, etc.

There's an oddball definition of "religion" that I like: "Religion is whatever ideas you beat up other people for". That's broad enough to include beating up people for believing in God. That's Atheism as a religion, as distinct from Atheism as a personal approach to the topic.

Different strokes for different folks. I've never physically gotten into anyones face to insist god is imaginary unless they first get in my face telling me I better pray or else. Live and let live covers much more ground than just life/afterlife. If you go out and fuck a chicken..go for it, but stay away from my chicken coup. I don't want chicken aids. ;)

Some people are evangelists even if they aren't evangelicals. It's a temperment thing. If someone is a screamer, they'll scream at anyone who doesn't buy their particular brand of truth. I've never run into a screaming atheist myself, so I hope they're rare!

Insecurity and confusion. Before becoming an athiest and critic of God, one should define God. A good athiest will always do that. Most athiests of today are driven by the hate against organized religions and Gods propagated by them.

There are assholes on both sides. Once you start making broad assumptions about a very large and diverse group of people based on those assholes, then you become one of those assholes yourself.

Im sorry to bust your bubble, however, I'm a agnostic and a real asshole. Just like God, if he exist.

It is so rude to push you beliefs on other people. atheists try and make you believe what they think? No.