The man, identified as Anwar Sadhik, was arrested under IPC 124 (A) (sedition).
Police said Sadhik, posing himself as a journalist attached to a regional daily, allegedly made derogatory remarks against Niranjan and his family in his Facebook post.
He was arrested based on a complaint by the management of the regional daily, whose name he used in the post.
A casual labourer at a local shop was arrested from his house at Chemmankadavu in Malappuram district in the wee hours today, police said.