The man has been arrested on charges of attempt to murder, they said.
Babu allegedly punched the journalist in the face while he was shooting the video of his purportedly picking a fight with a owner of a tea stall near the protest site after being asked for money for the food consumed, a senior police officer said.
The journalist has been admitted to the government Royapettah hospital, police said.
DMK and other parties had extended support to the protest over the issue of premature release of seven life convicts in the Rajiv Gandhi assassination case.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)