I’ve explained the caste system before and don’t have much time. Simply put, it’s a general description of innate qualities of people and not by birth, although generally those born in, for instance, military families, may be more likely to join the military. Or those born in families with generations of university educated members may continue the tradition.
It’s described in detail in the Bhagavad Gita. The modern understanding is not based very well on scripture; but western misunderstanding misses the entire point.
The real point is that people should do what they are suited to do by their nature, and there are rules governing the types of duties and responsibilities.
One problem (and most likely described further down the thread) is that there are some very aggressive and unscrupulous Christian groups who are pushing conversion on tribal and other poor, uneducated people, in a very offensive manner. This is not right, and I am not justifying in any way any aggression or violence. But the forcible aggressive type of conversion is not right.
If you are talking about attempts to convert by gun or sword, virtually all American sponsors of such missionaries would quickly repudiate their support upon learning of this.
If you are referring to hellfire and brimstone preaching of the hereafter, however, there is a well known adage about kitchens and heat. If it's mere man telling a fairy story, you need pay no mind. But if it's bringing to your recollection something that man has not entirely forgotten -- a sovereign transcendent spirit who has the right to punish as well as to be merciful -- I suggest you jolly well listen.