Police said Mohammed Harris Nalapad and his 10 friends beat up the man at a restaurant in UB City late last night after they felt offended over him extending his feet, cast in plaster, towards the table they were sitting at.
Nalapad's whereabouts were not known.
The man, identified as Vidwat, has been hospitalised, police said.
Nalapad, general secretary of Bengaluru District Youth Congress, is the son of Shantinagar MLA N A Harris.
Police said an FIR has been registered against Nalapad and his friends.
The MLA described the incident as unfortunate.KPCC president Dr G Paramaeswara tweeted Mohammed Harris Nalapad, general secretary of Bengaluru city Youth Congress, has been expelled from the Congress party for 6 years. "Atrocities in any form is not tolerated in @INCKarnataka. Legal actions have been taken against those responsible. The victim will be served justice," he tweeted.