Nah Hindi is the national language of India it's just the south where Hindi is not that widely spoken. As you know Indian states are linguistically divided, you have like a different language in different state ie. Marathi In Maharashtra, Bhojpuri in Bihar, Gujrati in Gujrat etc. In most states people can understand hindi due to the large movement of people from one state to another (office workers, govt staff, labourers etc).
I'm from Maharashtra but not a native but you can pretty much not know Marathi and still live there, almost everyone knows hindi fully or upto manageable standards.
This movement of people is not that high in south, so not much incentive for a hindi speaking culture to develop there.
Also you can say English is sort of a national language of India too as it's used like everywhere in our courts, schools, exams, in normal life etc.
All the political blabber, discrimination talks in news is due to the political parties ie. BJP and communist party being at odds.