I know some of you will answer, "because religions turn people into dicks", I paraphrase and boil it down to a general colloquial type response.
Richard Dawkins is the poster boy for the angry atheist. Why? Probably because he is like most of us and has discovered with compounded evidence that it is stupid to believe in a crazy god, in the case of the Old Testament's JEHOVAH and the whacked GOD THE FATHER who killed his own SON. To be honest, I don't believe Jesus ever existed.
I'm not looking to bother Christians and they've learned, in short order, not to evangelize me, therefore, I am not angry at them except when they VOTE, otherwise, we get along royal because they know I am a righteous "pagan" and consigned to the First Circle of Dante's Hell.
No anger is always appreciated by everyone. If a Christian is angry at you, don't feed them. If we get angry, we are just like the anger thrown at us. In this, I am a "better" Christian than a Christian asshole.