Qui Gon was the former jedi turned sith Lord Count Dooku's apprentice. Therefore i think he was a lot more loose with Jedi ethics.
He probably also new anakin would turn to the darkside but seeing the bigger picture was also the one who brought balance to the force by doing away with the sith. If millions of innocents and thousands of his jedi brethren died along the way it was the will of the living force.
Qui Gon is directly or indirectly repsponsible for the fall of the republic and the rise of the empire.
Don't forget if he did not take anakin from tatooine to be trained anakin probably would have never become a monster like vader, but Luke and Leia probably would not have been born. He would have eventually been freed as a slave along with his mother by Cliegg Lars and ended up a moisture farmer.
The jedi are flawed in oh so many ways according to the prequels. Because Yoda was Dookus master and he was yodas padawan. Qui gon was dookus student. Obi wan Was qui gons student and anakin was obi's.
Dooku and Anakin both fell to the sith because of flawed training and poor teaching by their masters.
Another irony of the prequels is palpatine needed Jar Jar's help to get those immergency powers that allowed him eventually to kill off the jedi and overthrow the republic.
Jar Jar being a weak minded fool was mind controlled by sidious.
He was supposed to act in Padme's stead when she was away under protection to prevent the war act, instead he did what she did not want.
At the same time Padme has to be the dumbest and most naive person ever to think backwater retard binks up to the task of being a senator from naboo.