As if Kakashi could do anything against Madara
Obito should know better
That's actually plausible. The statement "You let Rin die" seem at first contradictory to what Kakashi actually did. It's also common sense that Obito should know everything about Kirigakure because he had access of many information through Yagura. How do you take over a village and not know anything about it. That means he knew what Madara was doing all along, concluding that he never wanted to be Madara's ally in the first place.
That's actually plausible. The statement "You let Rin die" seem at first contradictory to what Kakashi actually did. It's also common sense that Obito should know everything about Kirigakure because he had access of many information through Yagura. How do you take over a village and not know anything about it. That means he knew what Madara was doing all along, concluding that he never wanted to be Madara's ally in the first place.
This could actually be the case if Kishi actually decides to go this route with the manga.