That was kind of the point of that scene wasn't it? It might even have been the most important scene that episode.

Airi asked him why he is doing all this, and he replied "because I want to complete the experiment." So she asked him why he wanted to do that, and he paused, confused for a split second, then chuckled as if it was obvious and said, "because I want to complete the experiment."

He has less free will than Misaki, even less free will than Sister Centipede, who displayed emergent behavior at the end. He's a ghost, maybe not even that. He's just an out of control Do-While loop.

He can't really think for himself, he can just complete his ordained task. He's forced to.