Yep, exactly. Salman trying to convince people that he is not biased is the funniest joke he tells.
No one is disagreeing that Rubina does wrong. Of course, she does! No contestant is perfect inside that house. But it's about HOW Salman chooses to react to her wrongs vs someone else's SIMILAR wrongs. If she does action A, he will yell and speak as if she has killed someone. If another contestant does the same, he either ignores it OR explains very calmly to them.
When the whole Jas and Nikki were bullying Rakhi happened, notice how calmly he explained to Jasmin that she was wrong. And then he flipped the WHOLE thing on Rubina saying she looked worst. And you could clearly see the anger on his face. It's bizarre. His obsession of pinning anything and everything on her is just plain bizarre.