@mishrakirti Yeah there is never an Aryan invasion, it's just some false history which the Britishers told. And for your question , Karn was not discriminated based on his cast but the discrimination was based on his worthiness. Karna is 'suta' putra i.e son of someone who is like a driver to the King. Karna was criticized when he challenged the Pandavas who are princes. There was caste system from Ancient period but people lived in harmony, it's just after the Arab and British invasions these cast indifferences occurred. That time there wasn't mostly any. Hope I clarified your doubt....Sorry for the late reply