In a recent class someone asked how a Buddhist monk could invite hatred and murder, as is in Myanmar. One might ask the same question regarding Christians who have murdered in the name of Christ; Muslims in the name of Allah. We expect such behavior from racists and ultra-nationalists, but not of Buddhists.
The short answer is: many people get caught up in greed, fear and anger stoked by misguided, self-serving leaders. The raw emotions fired by racism and nationalism trump religion and ethics.
