[Teru987]

I'm going to guess:
Obito blames Kakashi because, despite the Blood Mist being the ones that used Rin, Kakashi allowed those events to take place. Hence, "You let Rin die" is not a false statement.
I doubt Rin would betray the Hidden Leaf. Chances are there was foul play involved.
Kakashi was surrounded by quite a few Blood Mist shinobi. Chances are, being outnumbered and Rin being the target and her capture most likely leading to some tragedy for the Hidden Leaf, Kakashi had no choice but to kill her himself.
She might have even asked him to do it.
It's not necessarily a plot hole that Kakashi remembers none of this. Anyone that thinks it's easy to retain a good memory of you killing one of your best friends needs serious therapy or a wake up call. He passed out and likely had no idea what was going on.

More plots holes cause now everything that was told about kakashi is starting to become bullshit.

If you're my best friend, and my girlfriend gets bit by a vampire and you murder her with a wooden stake to save the world, I'm still going to be pissed at you for letting her get bit by a vampire.

First off Obito and Rin were never going out so its not really the same. If you had said that he let his friend get bit then that would make more sense.

Obito collaborating with Madara has nothing to do with him 'not facing the facts'. The facts are, the world is cruel and that cruel world led to Rin's death. Madara told Obito he dreams of a world without pain or suffering. This has more to do with Obito realizing there isn't 'blame' to be made for one person or one group of people but for the world of shinobi at all. If you think about it, it makes sense. What led to the Sand Village having a peaceful treaty with Leaf Village? The battle between Sand Village and Leaf Village which resulted in 3rd Hokage's death. What led to the Shinobi Alliance with even the Samurai coming out of neutrality to join the Shinobi Villages? Sasuke and Tobi's attack on the Kage Summit which ultimately resorted to Danzo's death. Obito is probably tired of a world where small victories are obtained at the loss of life.

Madara also said that you will be back and thank me. If you dont think that Madara wouldn't plan stuff out before putting them in to action then you might have a screw loose. He wouldn't just attack the First without planning it out, he had Kurama with him.

he idea is Kakashi had it the whole time but never 'unlocked it'.

I he had it then it was already unlocked! Sasuke didnt want to remember/believe that itachi was crying thats why it took naruto getting his ass kick for him to use the sharingan.