Power structures EVERYWHERE become violent when faced with existential threats
The caste system guarantees that those of the upper classes stay in the upper classes, and are not threatened by smart people in the lower classes who want to rise above where their caste had put them.
Eliminate the caste system, and everybody needs to actually use ENERGY and INGENUITY to achieve and retain status. This can be very threatening to the mediocre
I have heard some of the terrible things about the caste system.
Ms. Casey's Daughter