Qui-Gon left because of the celebacy rule of the Jedi which he explains to Obi-Wan with help from some Batman Begins lines, as for Obi-Wan, Qui-Gon dosn't take him from the Order, he leaves because he sees anger as a crutch to aid him if used sensebly, and finds Qui-Gon, a fellow Rogue to allow this in his training, however after he sees Darth Maul, a creature of pure hate and anger kill his master he renounces this belief and returns to the order, Yoda then dubs him a Jedi on merit of his actions.