> 1. The Sinhalese majority were given mandate by the British.
No. They were a simple majority so took control through elections. They felt discriminated against, and that the British favoured Tamils and Christians..
> 2. They used this mandate to apply incredibly discriminatory practices towards the Tamils.
True. mostly over language. Minorities in general were disadvantaged.
> 3. Constant rabble-rousing by Sinhalese politicians intermittently led to race riots, in which Sinhalese mobs carried out pogroms and murders against Tamils.
True, but this was on a small scale until after the war actually started. Other groups (such as Muslims and Christians) were also targetted.
if you read the article about the "progrom" it was preceded by the LTTE murdering a Tamil policeman, and intimidating others.
> 4. Due to almost laughably blatant policies targeting Tamils, such as an affirmative action policy designed to reduce the number of Tamil students at universities, a group of Tamil students formed a league to protest the matter. These students would become the forerunners of the tamil militant group
True to an extent, but the affirmative action was also targetted at helping poor and rural students vs affluent ones. The core of the system was basically giving extra points to those from schools and areas that did not historically get students into university. For the language based part, how is this different from race based affirmative action in the US? The idea was to boost numbers of historically underrepresented groups.
> 5. Further barbarism from the Sinhalese majority, such as the destruction of culturally important Tamil heritage (for instance, the destruction of an important library), seeding racial tensions.
Mostly the burning of Jaffna Library. Horrible, but not an excuse for atrocities.
> 6. A rebel group carries out an ambush against the Sri Lankan army, seemingly as retaliation for the assassination of one of their commanders.
That is roughly right. The race riots were horrible. I know a lot of people who were affected and traumatised by it. That does not justify doing the same back.
The LTTE was also utterly ruthless to Tamils who failed to support it. They completely wiped out other Tamil militant groups to consolidate their hold on power, they raised money from abroad by threatening people's families in Sri Lanka, they targetted Tamils in the armed forces.
Most ethnonationalism is a reaction to some real or perceived wrong. You will end up justifying everything on those grounds.
> The only consistent perspective that Sri Lankan commentators seem to provide in their support for the killing of civilians is their strong belief that Sri Lanka must be a Buddhist nation and that Buddhism has a special place in the state constitution
You are only reading bigots then. Most people who do defend it will tell you killing civilians was an inevitable result of war - collateral damage.
I know very few Sri Lankans from ethnic or religious minorities who support the LTTE or even feel that their actions were even remotely justified. I am mixed race (entirely minority, Tamil on my mother's side ) and Christian (as are most of my family). I have worked in a Tamil suburb of the capital city and many people there felt that they were oppressed by both the Sinhalese and the LTTE. I know people from all the major ethnic groups and religions and everyone opposes the LTTE.
You also need to take into account that the motive for the LTTE's violence was also racial oppression with Tamil people - the low castes by the high castes. I think this is why Tamils (both Hindu and Christian) turned to violence, while Christians from other ethnic groups did not (apart from the 1962 coup attempt) and Muslims (apart from the Easter bombings which were an exception there was the odd riot) rarely did. That opinion comes from talking to people who know Jaffna well (including my father who used to run the civil service in the peninsula).
> The sexual violence that seemingly became routine for Tamil
What makes you think it was routine? There is no evidence that it was encouraged as policy or a weapon or war (as say happened with Bangladesh broke from Pakistan, among other instances).
> We treated the Tamils like subhumans, actively discriminated them into poverty and kept murdering them and rioting in their areas. Now they're fighting back, so we're justified in committing genocide
That is a gross exaggeration. My mother would have laughed at the idea that she was treated as subhuman, as would my relatives on that side of the family, or my Tamil friends.
Discrimination is no excuse for terrorism or ethnic cleansing. Would black Americans be justified in bombing white majority areas, driving white people out of black areas etc? it is far more true to say they were historically treated as subhuman than that Sri Lankan Tamils were!