I have an extremely different point of view....
KKK is a game show at the end of the day and all participants are competitors. Arjun won the K medal and had all the right to use it in any way he pleases. Yes I was upset that he chose Sourabh, yes I was even more upset when Sourabh was eliminated. But from a strategic point of view what Arjun did was right - eliminate competition.
This reminds a lot about last season. I dearly loved Tejaswini! It was unfortunate that she had to leave due to an injury. I found it mean that no one would sub for her even tho she helped everyone when she could. But from a game perspective it was justified. Everyone was there to win!
At the end of the day, along with performance strategy will also matter. If the show was genuinely bias they wouldn't have paired Arjun with Anushka and then Mehak because the two of the clearly are weaker contestants.
Arjun's behaviour outside the stunts in my opinion is not derogatory. He is only making fun, and everyone understands that it is a joke. At s point in time in the show everyone would be a subject of mockery.
I am not a fan of Arjun but I feel that the hate is unnecessary. I hope Sourabh can come back soon!