Blackshirts are members of the anti-religious, atheist quasi-political organization Dravidar Kazhagam in Tamil Nadu, founded by "Periyar" E V Ramasamy.
[1] Periyar was pro British, anti-independence activist, who showed his disgruntlement with freedom struggle using black flags and shirts.
[2] Periyar wanted to uproot caste sentiments and superstitions prevalent in Tamil society.
[3] This has its origins in the banning of black flags as a protest tool in Tamil Nadu.
To circumvent this ban, members wore black shirts.