I found no confirmation of the events described in the first link on the net. It may be due to poor Google skills, or something else. If there's something out there, I'm sure someone here will be able to find it. However, the text
does mix myth with history (Like saying the genocidal invasions started on the same day that Gautama Buddha attained enlightenment, and quoting a book written 600 years after the fact.).
It also quotes from a book by a man called S.J.Gunasegaram, which they say prove what they claim. The only reference to this person on the internet is on a site called tamilnation.org (where there are som articles by him, including the 'book' mention in your link). Three of five references to the article in your link is from tamilnation.org.
As a generalization, Tamils are very biased towards Buddhism.
From the article you linked to :
The oppression of Dravidian Shaivites by Aryan Buddhist Sinhalese continues to this day. The enslaved black Dravidians are now, thanks to the Global Black Nationalist movement, receiving substanital help from Blacks in South Africa and America in their struggle against White Aryan Buddhist tyranny in Sri Lanka.
I have no idea who the Dravidian Shaivites are, so I asked Google. I got around 15 hits, none of them explaining very well who they are, except that they are a Hindu sect. None of them mentions Sri Lanka.
Trying the two words seperatly, Wikipeda tells me this :
Dravidian may refer to:
A group of people who came through Arabia to settle on the Asian mainland at the Strait of Hormuz and on the Indus river in what is now Afghanistan. These people were driven southward into India. Some scholars attribute this to a later 'Aryan invasion.'
Dravidian languages, including the Tamil, Telugu, Malayalam, and Kannada languages spoken especially in southern India and northern Sri Lanka.
Southern Dravidian languages, a major grouping of the languages
Dravidian race, a member of any of the peoples that speak one of the
Dravidian languages , especially a member of one of the pre-Indo-European peoples of India
A political movement encompassing a number of different parties that appeal to speakers of the Tamil language
Shaivism
http://en.wikipedia.org/wiki/Shaivites
Śaivism, also transliterated Shaivism and Saivism, is a branch of Hinduism that worships Siva as the Supreme God. Followers of Śaivism are called Śaivas or Śaivites.
Originated in India, Śaivism has appeal all over India and is particularly strong among the Tamils of Southern India and Sri Lanka. Some traditions credit the spreading of Śaivism into southern India by the great sage, Agastya, who is said to brought Vedic traditions as well as the Tamil language.
To conclude this, I believe we are looking at Tamil propoganda, used to create animosity between Tamils and Buddhists. If I am wrong, it shouldn't be too difficult to prove me wrong.
As for the role of Buddhism in the Japanese Empire pre- and during WW2, I think you'll find that Shinto and the Confucianist inspired Bushido ideal had much more to do with how things turned out. Although it's a shame how the Japanese Buddhists kept their mouths shut about what was going on, many Buddhists were also imprisoned by the government because they spoke out against the war.
How do you know I'm a westerner, anyway?