From the time, Ruhaan became PG in Mishti's house, we can see that he is the guy "Jise Zindagi ki samaj hai duniyadari se zyaada. The way he comforted Pari when she is feeling low about disappointing Mishti on terrace is commendable. When he motivated her to be herself and to evolve in her own self, it shows that he is a self-assured man. He tries to be in peace with his own self. That is what makes him realize and understand his own failings and at the same time be empathetic towards others flaws. Ruhaan takes time and analyzes the reason behind a person's behavior before reacting to it.
People in the forum were like he has no self-respect as he stayed back after so much humiliation. I have a different take on this. Earlier Ruhaan used to give it back to Mishti as he thought her behavior sometimes wasn't appropriate. But during the flower incident on road, he could see that he affects Mishti in a certain way. The myriad of emotions that Mishti conveyed through her eyes spoke enough to Ruhaan. During his stay as PG, he saw how over-protective Mishti is for her siblings. When she lashed out at him, he was calm coz he knew he was not wrong and didn't give it back coz he knew she was in pain due to the incidents happened and frustrated over her helplessness about Ruhaan's existence and its effect on her.
Why should Ruhaan leave? To prove what? Everybody out there knows that he is not at fault and Mishti will also realise it once she is calm. His self-respect didn't get tarnished, but it was Mishti's not so perfect self that emerged out. For me, he is a man who carries himself with dignity, who follows his heart, a heart that is guided by his strong moral conscience.