Good luck sir
Good luck on your lawsuit sir.
I have to admit, in HR's defense (not much of a defense but still), it is rather unbelievable that a) There's still an alive and well caste system and b) That people would leave the country but bring the caste system with them. I mean, *I* believe it but would not be surprised if some simply didn't believe it.
Second issue in the US -- discriminating based on race, gender... well let me google it... "race, color, religion, sex, national origin, disability, or age" is illegal. Caste is none of these, so if the HR department views their goal as merely avoiding illegal behaviors, they did. I've seen both, some HR departments are all about "compliance", if they are compliant with the relevant laws that is it, job done; other companies do have HR truly try to help work out interpersonal disputes and so on to help have a more harmonious workplace.