Bunk. The "caste system was not an arbitrary set of divisions or inequalities established through force or aggression"???? Total rot. That is exactly what is was, and remains today whereever it is found.
True that ==>IF<== you could have a caste system where everyone was born into the bottom caste by law but could work their way up over life -- that would have interesting possibilities for sure -- but depend on it, the politically connected and those born into wealth would bend and warp such a system in just a few generations so that you would end up with the same cruddy caste setup as has been encountered in history and as exists today in India.
As for the "the Roman Church, containing mostly peasants" blah blah -- that is not where their power came from. It came from the fact that 2nd born sons of the nobility entered the Church since they would not inherit the estates and title. Thus the leaders of the Church were nobility -- they didn't HAVE to "claw their way to the top".