Spade, of the instances you have given (or rather, BBC has given), only Sri Lanka stands up to scrutiny.
We know a Tamil couple from Sri Lanka (he is a psychiatrist, she is a neurologist). They tell me that in Sri Lanka the discrimination against Tamil minority is written into the law. Thus Tamils need more qualifications than Sinhalese to be admitted to Medical school, to be eligible for employment etc.
So it is not really Buddhists going to war against Hindus, it is just Sinhalese being jerks and discriminating against the Tamils.
It is more really discrimination based upon the language rather than the religion, in that even if a Tamil converts to Buddhism, he won’t be free from discrimination, and even if a Sinhalese converts to Hinduism, he still won’t be discriminated against.
Contrast this with Saudi Arabia or Egypt, where if a person converts from Christianity to Islam, his life will immediately change for the better. So here I will give you half a point, not a full point. It is not the Buddhists discriminating against Hindus, but Sinhalese (who are predominantly Buddhist) discriminating against Tamils (who are predominantly Hindu). This can’t be blamed on Buddhism, any more than Stalin’s atrocities can be blamed on Atheism (he was a Communist, not an Atheist).
In the 14th century Buddhist fighters led the uprising that evicted the Mongols from China
Mongols had no business being in China. So I don’t think there is anything wrong in Buddhists throwing the bums out of China. Buddhists are peaceful, they are not pacifists. Even a peaceful person may take up arms in self defense.
Same as the Buddhist monks were behind the uprising in Tibet against the Chinese government. They were responding to oppression, there is nothing wrong in fighting to oppose oppression.
In Japan, Buddhist monks trained Samurai warriors in meditation that made them better fighters
They were teaching medication, they were not fighting anybody.
In the twentieth century Japanese Zen masters wrote in support of Japan's wars of aggression. For example, Sawaki Kodo (1880–1965) wrote this in 1942:
There may well have been a few Buddhists who may be warlike (though I think most of the support for Japan’s wars of aggression came from the native religion of Shintoism and not Buddhism). You may find isolated instances of Buddhists promoting war, perhaps even unjust war. As I said before, there are hotheads everywhere.
However, I still stand by my opinion that of the major religions, Buddhism is by far the most peaceful of them all.