Some time back, I knew someone in Pittsburgh who has since made Aliyah (in fact I have known several, but I won't identify this one further). We had gotten to know each other well enough that I considered him a friend, the kind where we talked and argumed a lot about philosophy. An Orthodox Jew, he was representative of one of the many positions possible in Judaism, just as we all might represent some group of people like us in some way. More importantly though, the ideas and tendencies of humanity as a whole are realised to some extent in each of us - while culture may modify us reasonably far, most of our inclinations are in common and come with the species. I often argued with this particular person about identity; he strongly believed in nationalism, particularly Jewish nationalism but he also believed that those of other cultures should have their own versions of this. His notion of human ethnicity was tied to this - he didn't have the "there are racial divisions in society but they're hierarchial, there's a lot of blending, and when you get too close to any part it's hard to see the borders" perspective that I and many others have - his concept was more that there are a set number of types of peoples, there are strong and clear lines between them, they all have strong personality tendencies and share common responsibility for their own actions (placing him in the set of people who will forever be angry at anyone German for Shoah, even likely hundreds of years in the future). A specific conversation I recall with him related to association - he held that it was not inappropriate for someone to only hire, do business with, serve, or otherwise associate with others in the same "people" as them.
Moving (finally) to Sri Lanka, let's first lay some historical background. Sri Lanka is an island off of the east coast of the Indian Subcontinent. A former part of greater India (as were Pakistan and Bangaladesh), it was part of the territory so defined by being captured and colonised by the British (in this case, colonised means an intent for prolonged wealth extraction combined with being brought into British culture and having modern infrastructure of various sorts installed). Like most of India, it had its own distinct ethnic group (the Sinhalese) who had controlled the area in their own state before colonisation; the British complicated the situation by both being present themselves, but also bringing large numbers of Tamils (another ethnicity primarily residing in the nearby area on the mainland called Tamil Nadu) as farmers. Moving forward into the late 40s, like the rest of India they became independent, and unfortunately for the Tamils who had been on the island for several generations, the Sinhalese dominated the independence movement, created the new state, and using both state and cultural institutions to systematically exclude the Tamils from economic and cultural life. Not long later, a very long and slow civil war broke out as formerly peaceful Tamil parties were replaced by more militant ones as the peaceful parties failed to make any headway against the Sinhalese majority and that majority failed to serve the broad interests of society. Eventually, one organisation, the LTTE (Liberation Tigers of Tamil Eelam, commonly called the Tamil Tigers) closed all other Tamil parties/orgaisations on the island (often through assasination), raised a military, and, with the desperate but uncomfortable support of Tamil people, began experimenting with a number of tactics widely considered to be atrocities (occasionally emulated by Al Qæda and other militant groups). Over the decades since, battles went back and forth between the Sri Lankan military and the LTTE, with frequent assassinations, suicide bombs, and the like. The LTTE drew on funding sources from organisations in Tamil Nadu (support people in your ethnic group for they suffer) and expatriate Tamils all over the workd (significantly in Britain and Canada), despite antiterrorist-funding laws designed to cut them off in each country. The international community played its part in having the conflict drag on - every time the Sri Lankan military came close to absolute victory, they were stopped by political forces calling for a cease-fire, giving the LTTE the time to withdraw and regroup to rebegin the cycle. Only the willingness of SL president Rajapaksa to temporarily ignore international opinion and seize victory when it came close led to the eradication of the LTTE (which to the end performed atrocities on both Tamils and Sinhalese).
The lessons we take away from this are not that the LTTE was bad - it was an organisation that portrayed many of the worst traits of humanity. Instead, the problem lies in what made it possible for a desperate and abused people to spawn such an organisation that came to lead them to struggle. In a more ideal world, the Tamils still needed a paramilitary force to protect their interests - a docile people willing to take any abuse usually is severely abused, although a force less nasty and more willing to negotiate when SL finally got the point and did not treat Tamils as second-class would have been sufficient. Once a group is radical enough to fight, it's not easy for sensible and cautious voices to win out against groups pushing ever more radical agendas; the LTTE destroyed all peaceful Tamil parties and eventually all the more sensible militant ones in the early years of the struggle. Another lesson, an important one that ties into the introduction, is that it is not only the SL government that bear the blame for the abuse of Tamils - the Sinhalese people, through widespread preferences in dealing only with themselves, racism, and poor treatment of the Tamils were just as responsible for making Tamil life very difficult in Sri Lanka - they longed for days they could not remember where there were only Sinhalese on the island. It is this strong ingroup/outgroup mentality that is dangerous to humanity - when the ideas that the person I called friend become systemic and make worse enough the lot of someone in society, even should the government have nothing to do with it, there is a strong impetus for the excluded parties towards stronger action than accepting the societal institutions that hem them in (democratic or not). Often the resistance structures they create are very nasty. This is a common trend in humanity; it does apply to Palestinians and Israelis, but also to Black nationalism in the US, many parts of the former Soviet Union, Africa, etc.
A final pair of lessons - outsiders, particularly those that don't appreciate nuance or don't understand the complicated history of a conflict, should be wary of involvement. The LTTE-SL conflict was drawn on by effective Tamil use of PR to exert international pressure to prevent SL victory several times, these same external forces being quiet throughout the duration of more stalemate times of the conflict. It is very easily to be manipulated by these things - a firm intention towards peace can in some cases lead to actions that prevent it. Secondly, those with blood ties to the conflict often have a poor understanding of it because they're trying to be a "good Tamil" or "good Sinhalese", believing the propoganda put out by either side (including falsified histories, in some cases). The best conversations with people who know about the conflicts generally began with "it's complicated", not out of a juvenile attempt to be even-handed as a conscious goal, but rather because an honest assessment of the history and situation is not easily covered in a few sentences nor does it have a clear hero.