Literally everything Haruji said is correct. Doubara is clearly taking advantage of Mio's distress. The only reason he's interfering is he knows if she faces reality than he loses his excuse to interact with her.
No, Doubara IS NOT TAKING ADVANTAGE of Mio's feelings.
They're just opposites, two ways of dealing with what's happening with Mio.
Yes, Haruji's "way" is necessary. Not as forceful as he is and he is being that forceful because he also lost it. He is also "in the wrong" as much as Mio's for not being able to deal with the situation. At the same time Doubara's way is also equality as necessary and valid, Mio needs time to accept the reality by herself. Anyone thinks that now she "admitted" it everything is alright? That she is "cured" now? Of course not! And does anyone expects Haruji to be able to stay by her side, give her the support Mio needs?