Every community; be it religious, ethnic, racial or cultural is composed of a spectrum of attitudes - from benevolent, merciful, caring, to ruthless, intolerant, bigoted and violent radicals, it is a mix. No group is an exception to that mix. My guesstimate is the violent intolerant ones are less than 1/10th of 1% of any group including the Atheists.
Score keeping does not solve the problem, the world has witnessed ruthlessness from Atheists to Zoroastrians and every one in between. They have massacred people, butchered people and have forced people to do things against their will. Singling out any group is downright ignorant; no one can cast the first stone.