Fattu aadmi hain saala. Always a part of bhed chaal/herd mentality. Ideally, he should have given the dose to Rahul too, but looking at the support Rahul is getting from some of the housemates, he immeadiately went with the flow. And his dumb explanation in the end would be that he did it bcoz he wants to highlight his friends by insulting them in a task. He used to do the same thing to Pavithra and Jaan too, which confused them and audience as well.
On the contrary, RV never bowed down to the peer pressure and stood by Arshi when she was alone and isolated. He was also the first one to go to Arshi during the break to console her. Seeing him only, others followed to sit with her.
Very impressed with ppl who don't throw thier own ppl under the bus when under pressure, rahul may have alterior motives behind this perhaps he wants to solidify bond with arshi as he plans to use her shoulder to fire on rubina and nikki but anyways it was sweet of him and yes only after seeing him rest of contestants followed and stood around arshi..