i believe caste is a useful and good tool. this conclusion i have come to after considerable analysis of the data available.
casteism, on the other hand, is morally reprehensible, and is the same as 'secularism' in india: discrimination based on some un-objective criterion. casteism discriminates against some castes, 'secularism' discriminates against hindus. both completely wrong and immoral.
i too used to think that caste was bad. no, it is a reasonable organizing principle of society. the problems began with the british who built up a) the manusmrti, b) the caste system as founding principles of hindu society. neither is. caste is merely a recognition of fact that there are micro-organizations that social humans prefer to belong to. caste exists quite powerfully in every human society, especially in christist and mohammedan societies, except they dont call it caste.
caste has been useful in making hinduism a distributed system, thus more robust in the face of external invasions, unlike the centralized buddhist system, easily overthrown by mohdans.
this is the reason christists attack caste, because atomized, un-organized hindus are easier to convert. dramatic instance in kerala: OBC ezhava/thiyyas were attracted in large numbers to christist institutions in the years between 1819 and the time of the creation of the SNDP yogam. in fact, so much so that the vast majority of christists in kerala are ezhava converts. but one the SNDP yogam, in effect (although not in intent) an ezhava organization, was formed, ezhava conversion has slowed to a trickle, as caste feeling and pride and support has reduced the charms of the blandishments dangled in their faces by missionaries.
the fact of the matter is that most hindus would not convert under normal circumstances, given that they can see that christism is fundamentally deficient, illogical, and absurd. (i have that 'absurd' on authority of early church bigwg tertullian who said,
Natus est Dei Filius; non pudet, quia pudendum est: et mortuus est Dei Filius; prorsus credible est, quia ineptum est: et sepultus resurrexit; certum est, quia impossibile
(Translation: "The Son of God was born: there is no shame, because it is shameful. And the Son of God died: it is wholly credible, because it is innappropriate. And, buried, He rose again: it is certain, because impossible")conversion comes when people are sick, poor, starving, or otherwise vulnerable.
here is an example of how caste members sticking together has helped them: