[foolinaround]

From your writing above, I can see you are not from Tamil Nadu and that you need to educate yourself more.

Would it blow your mind if I told you that Shiva (or Vishnu) was not even worshipped by Tamils or in the ancient literature till it was brought in from the north?

The real religion of the Tamils is akin to ancestor worshi. Later, all the religions started invading and setting up roots ( actually Buddhism/Jainism took roots before current Hinduism came down ).

[eklavya]

That seems to be patently false. The oldest Tamil literature is Sangam literature (except Tolkāppiyam which is about grammar and contains influences from people all around India) which also contains poems for Vishnu, shiva, Durga. Buddhism and Jainism came way later.

[foolinaround]

AFAIK, Shiva is not mentioned at all in Sangam literature. The gods in both these cultures had similarities and a synthesis happened down the road.

for example, Murugan was the primary god and later assimilated with Shiva etc.