Why the anger??

I have not been so lucky to have amassed comments like so many other atheist bloggers around the web, but I get a few. I have been lucky in the fact that they have been nice, even when disagreeing with me. 

So when I have the opportunity to read from other bloggers, I am amazed to see such hatred and vitriol coming from religious people. Of course this does not represent the majority, and I find most are cordial, but I have to wonder what is going on in the heads of the few who shout just mean things about the people who do not concur. Do they think that it will make the blogging stop? Do they imagine to persuade anyone?

Lastly, why do people have dramatically defensive behaviors when finding someone declaring their beliefs to be false? I do think they are related.