I lived in your country, so I've seen how the untouchables and Christians attempting to advance themselves are treated and regarded by your society. It is not this rosy picture you are attempting to paint. I've never seen such abuse, mistreatment and misery of human beings like I witnessed in your country.
In fact Modi himself knocks out your statement -- he's an OBC -- other backward Caste
There are millions of castes within castes. But generally the political castes are beholden to the Hindu Brahmin religious leaders who may or may not be politicians.
Modi represents the surge in radical Hinduism that seeks to purge India of everything 'foreign', including religions that are not Hindu. The Christians I serve are frightened about what they already are seeing the Hindu mobs chanting and saying they are going to do to Christians with "Modi's blessings".
They have good reason to fear.
Christians are not discriminated against -- look at the Christians in Bombay in various companies who do very well. Christians who are new converts in the village areas, yes, there is discrimination as you point out, but don't make it a blanket all bad (and it's not a blanket all good either)