JESUS DUDE.
Huel took the pot. Jesse then realizes this. Jesse then realizes Huel took the ricin cig. He then knows that walt put a fake ricin cig in the roomba. He then realizes that if walt did that, it was because he was covering up for the fact he poisoned brock. Jesse knows Walt is the king manipulator - did you see the monologue? - and he knows that walt manipulated him with the ricin cigarette and how he did it. He's had it - especially because he knows Walt poisoned Brock.