Former India opener Gautam Gambhir slammed Test skipper Virat Kohli over his outburst against a controversial DRS decision during the third Test against South Africa, saying his reaction was immature and he is setting a bad example for budding cricketers. Kohli, his deputy KL Rahul and off-spinner Ravichandran Ashwin made some unsavoury comments about umpiring and technology in stump mic …