I got irritated by an article in the Spectator by Jackie Mason Why you never hear Muslim jokes (http://www.spectator.co.uk/article.php?id=7317&issue=2006-02-11). Of course, its intended as Jewish humour, the idea that Jews are naturally peace-loving/reasonable/cowardly etc. But its of the same type as a lot of more serious articles that claim that somehow some ethnic groups/religions/non-religious beliefs are intrinsically peace-loving, in a way that other religions (normally Islam) are not.
This prompted me to produce a brief list of modern (WW2 and later) examples of brutality in a variety of religious and atheist societies:
Christianity: terrorism (IRA, Basque ETA), massacres (Lebanese Phalangist militia, 1982), ethnic cleansing (former Yugoslavia)
Hinduism: terrorism (Sri Lankan Tamil Tigers)
Judaism: terrorism (Stern gang, Irgun), religiously motivated murder (Yigal Amir – killer of Yitzhal Rabin, Baruch Goldstein – shooting in Hebron)
Atheism: genocide (Nazis, Khmer Rouge), mass murder (Stalin, Mao)
This is just a brief list, and more knowledgeable people could probably add to it, particularly for Asia. Im also not trying to argue that all these examples are equally bad, and some might even be claimed as justified (e.g. pre-State of Israel Jewish terrorism). My point is only that no tradition is exclusively, invariably peaceful and that all religions (and atheism) can turn to violence in particular circumstances.