Sinhalese youth thought it was a problem with the system and rallied around JVP to create ideologically different economic system whose justification was urban vs rural discrimination . Tamil youth rallied around ethinic dogma to create a mono ethnic political system whose justification was Tamil vs Sinhalese discrimination. When people speak about discrimination it is everywhere. They discriminate each other base on religion, gender, class, creed, race, color you name it. Even within a single family there are discrimination.
Some parents treat their sons better than their daughters.
Even today in India if you are a female fetus you will not live to see the light of the world. As such one can see how pervasive this discrimination is. A Black Tutsi who fights a Black Hutu in Africa fight due to their clan or tribal differences. When the same Hutu and Tustsi migrated to U.S.A. their tribal differences evaporate, skin color takes its place. Both of them get together to fight White Caucasians' discrimination against Blacks.