User blog comment:Master Sima Yi/Assassinews 05-08-'14 – Assassin's Creed: Rogue announced/@comment-89.142.72.92-20141020153716/@comment-413232-20141020233445

I just don't see why Shay would leave the Assassins because they made him kill innocents (you're assuming it's because he doesn't believe in the Creed and won't kill for it, when there's nothing to suggest that)

I read everywhere that he have doubts and can't keep questionning the Creed. ex: "'If Everything is Permitted, How Everyone be safe?" In order to kill someone, even more an innocent, you need an unshakable faith in what your are doing, no ???

and then proceed to straight-up murder random people under the pretense of "I'm a Templar now, lol" 

I never read anything telling that there will be a mission involving Shay murdering random people, the devs said it will be a possibility given to the player during regular gameplay. During your gameplay, you can make Shay run in circle during four hour, it doesn't mean that he was a fan of Jogging. For me, the only canon things are the missions and the cinematics attached to it, how you play the rest means more about you than the character you are playing with.