Is my impression that animosity towards Muslims isn't as much in the south of Ind, and why is that?
It's complicated but in summary -
1. Different histories - muslim rule didn't happen to a great extent in the south and south was largely ruled by their own indigenous empires. Therefore there's no religious polarisation due to historical elements. Islam spread in the south through early Arab traders and merchants rather than through conquests.
2. The muslim population was concentrated in the north western and eastern parts of British India and friction and riots between the two communities (hindu and muslim) happened where the hindu and muslim majority regions mixed and not in the south which is far away from either Pakistan or Bangladesh.
3. Because of the same geographical location, south wasn't exposed to the partition violence and therefore less polarisation against the other whereas I'd imagine Punjabi hindus and muslims, and Bengali hindus and muslims would be polarised against each other due to what happened during the partition.
4. Different cultures - They do differ in religions and obviously each region has its differences but Pakistan, northern India and even Bangladesh to an extent have a lot in common as they speak the same family of languages whereas the south speaks a totally different family of languages. Cuisine also differs and even in the way people dress.
Put simply, you would be able to get by if you, as a Pakistani, were to be air dropped in any part of northern India but south India might look like a completely different country to you because the language would be unintelligible unlike hindi and the food would be completely different and rice based whereas Pakistan and northern (particularly north western) India is wheat based. Bangladesh I guess is mixed in some ways because eastern India tends to be rice based like the south. I suppose familiarity breeds contempt and that's one of the reasons why Pakistan and north india share contempt for each other while it's largely unknown territory for Pakistan and south India.
4. Social reforms also started early in the south I think, particularly in places like Tamil Nadu and Kerala. Radical anti religion and anti caste social reformers changed the way people think and each state has a specific culture. TN for example has a strong ideology of Dravidianism, and rationalism (which is just a euphemism for atheism) is a strong component of it. Doesn't mean all the people are atheists, but just that people aren't so hung up over religion, you can openly talk against practices in hinduism and criticise it and still win elections. Meanwhile Kerala has a strong culture of communism and as you might know, communism has strong atheist undercurrents to it.
All this doesn't mean everyone is atheist in south india and you will find many religious hindus and south india is home to most of the old traditional temples in India. But people are probably the least uptight about religion in the south than anywhere else in the subcontinent. And the results in the latest PEW survey about India also revealed the same. All this contribute towards far less polarisation against muslims in the south. Inter caste polarisation is much more than religious polarisation in south india. In fact, the hindu muslim issue isn't even a talking factor in our elections.