Oftentimes, the Angry Atheist has been brought up with a religious mindset (usually Christian) which he/she has abandoned for intellectual/emotional reasons. But the painful feeling of having been raised on "lies" and "fairy-tales" has left the person very bitter toward all religions and religious people. And therefore, the Angry Atheist will essentially pick fights for philosophical vengeance, targeting religious laypeople and often avoiding debates with intelligent religious leaders capable of destroying their arguments.
An unfortunate side-effect of this out-going hostility, is that religious people will often attribute the attitudes of this minority to all Atheists, causing a negative stereotype to be formed.
Notice how critics of capitalism aren't called "angry socialists", critics of modern liberalism aren't (or at least shouldn't be) called angry conservatives, etc.
Whenever someone deals with religion, however, he must don kid gloves.
Of course, there will always be those immature twats who take it to the extreme- i admit Brian Flemming is probably one of them. But you still shouldn't discount every one of their messages - keep an open mind! (though not too much so)
It should be noted that the vast majority of religion-critics don't "hate" religion - they're just tired of its near-immunity to criticism and debate.
Another example: the drug peyote is normally illegal, but some native americans out west are allowed to use it for one of their religious rituals - also, voodoo worshippers of a certain haitian-american sect are allowed to sacrifice certain animals (i'm not making this up)
It's weird how the moment the "faith" cover is given, a person's actions are suddenly almost off limits. Somehow, we've just agreed as a society that that's how we should work. And anyone who questions this norm is quickly labeled an "angry atheist".
Odd, don't ya think?