Mohan,
As Ragahavendar had mentioned, the song was one of the high points of the movie. From your post, I infer that you have not watched the movie. The story is that NT would be in hiding and under disguise pretending himself to be a mentally unstable man. So his costumes were designed in that manner. In fact he would ride on a donkey.
Well the political undercurrents were strong and when the movie came out [Aug 2nd,1975], the emergency was one month old and Perunthalaivar had taken ill and confined to the bed. So naturally the song received a huge response.
Regards