Resisting these "evil impulses" is itself a Good action, or it would not result in an alignment shift.

And, once again, in a world running on D&D, Jim should, in fact, be arrested - because otherwise he will commit Evil acts. If the authorities have discovered a way to persuade Evil characters to act Good - perhaps with threats of punishment or magic - then good for them, and I doubt a Good character would object, but that is not the case in the example given - these are Goblins, and without any reason to privileged the hypothesis that they have somehow been induced to act for the good of society, stabbing them is better than allowing them to continue harming others.