People of any region tend to be antagonistic towards crude attempts to force a foreign language and culture upon them. Hindi has no common ancestry with South Indian languages like Tamil. In fact, Hindi-Urdu-Farsi is from the same language family as English. Therefore, Hindi is just as foreign as English to South India and therefore it makes much more sense for South Indians to speak their native tongues and a useful foreign language like English or perhaps Mandarin in the future rather than be forced to learn Hindi.