Why is Karan roasted by his own colleagues in the industry?

Karan Johar is one of the most senior and celebrated personalities in the film industry with a career spanning over 26 years. However, there have been instances where KJo has been brutally roasted by B - Town celebs, especially actors from the younger lot like Ranveer Singh and the ones from his generation, wonder why? 
So Karan is quite famous for drilling out controversial statements from his guests whom he calls on Koffee with Karan, his talk show. They are also asked to ‘rank’ celebrities based on their acting ability and looks which is absurd as it hurts feelings. Karan has also been tagged as the biggest gossipmonger by his colleagues. Tired of dealing with Karan’s ridiculous questions, celebs have decided to drill Karan back.
After the Boycott Bollywood movement, the next season of Koffee with Karan looks far-fetched with Karan facing flak for almost anything and everything he touches.