Obito don't care about kakashi's reasons, his not gonna ask him why he killed her.
Obitos words were literally "..Because you let Rin die" not " why you killed Rin"
and when Kakashi said "ain't you gonna blame me, nigga?" he was like "nah,is cool. i don't care about a reality that imma change soon enough"
This is what's it all about, The moment Obito saw Rin die he rejected that reality and everything else that comes with it. He even rejected his own identity and re-write it with whatever else because who he is doesn't matter in this reality.
He only sees himself as a tool capable of turning a dream into reality, A dream where all that survived is Happiness,love and fuckin' rainbows which was clearly pointed out in that chapter.
Am having mixed feelings about this whole miss, like i used to hate naruto alot but right now naruto fulls under my category of "too bad, it's actually good"